diff --git a/app/assets/javascripts/boards/components/board_new_issue.vue b/app/assets/javascripts/boards/components/board_new_issue.vue
index 8d84c1735b8..17651b93728 100644
--- a/app/assets/javascripts/boards/components/board_new_issue.vue
+++ b/app/assets/javascripts/boards/components/board_new_issue.vue
@@ -130,7 +130,7 @@ export default {
             Submit issue
           </button>
           <button
-            class="btn btn-default pull-right"
+            class="btn btn-secondary pull-right"
             type="button"
             @click="cancel"
           >
diff --git a/app/assets/javascripts/deploy_keys/components/action_btn.vue b/app/assets/javascripts/deploy_keys/components/action_btn.vue
index b839b9f286f..aff31062906 100644
--- a/app/assets/javascripts/deploy_keys/components/action_btn.vue
+++ b/app/assets/javascripts/deploy_keys/components/action_btn.vue
@@ -18,7 +18,7 @@
       btnCssClass: {
         type: String,
         required: false,
-        default: 'btn-default',
+        default: 'btn-secondary',
       },
     },
     data() {
diff --git a/app/assets/javascripts/environments/components/environment_actions.vue b/app/assets/javascripts/environments/components/environment_actions.vue
index 16bd2f5feb3..e25ce6054af 100644
--- a/app/assets/javascripts/environments/components/environment_actions.vue
+++ b/app/assets/javascripts/environments/components/environment_actions.vue
@@ -57,7 +57,7 @@
     <button
       v-tooltip
       type="button"
-      class="dropdown btn btn-default dropdown-new js-dropdown-play-icon-container"
+      class="dropdown btn btn-secondary dropdown-new js-dropdown-play-icon-container"
       data-container="body"
       data-toggle="dropdown"
       :title="title"
diff --git a/app/assets/javascripts/environments/components/environments_table.vue b/app/assets/javascripts/environments/components/environments_table.vue
index 22863e926d4..e48601882fc 100644
--- a/app/assets/javascripts/environments/components/environments_table.vue
+++ b/app/assets/javascripts/environments/components/environments_table.vue
@@ -117,7 +117,7 @@ export default {
             <div class="text-center prepend-top-10">
               <a
                 :href="folderUrl(model)"
-                class="btn btn-default"
+                class="btn btn-secondary"
               >
                 {{ s__("Environments|Show all") }}
               </a>
diff --git a/app/assets/javascripts/ide/components/new_dropdown/index.vue b/app/assets/javascripts/ide/components/new_dropdown/index.vue
index 769e9b79cad..19b8429ce37 100644
--- a/app/assets/javascripts/ide/components/new_dropdown/index.vue
+++ b/app/assets/javascripts/ide/components/new_dropdown/index.vue
@@ -56,7 +56,7 @@
     >
       <button
         type="button"
-        class="btn btn-sm btn-default dropdown-toggle add-to-tree"
+        class="btn btn-sm btn-secondary dropdown-toggle add-to-tree"
         aria-label="Create new file or directory"
         @click.stop="openDropdown()"
       >
diff --git a/app/assets/javascripts/ide/components/repo_commit_section.vue b/app/assets/javascripts/ide/components/repo_commit_section.vue
index 0f403ce63f3..7d4b5b45940 100644
--- a/app/assets/javascripts/ide/components/repo_commit_section.vue
+++ b/app/assets/javascripts/ide/components/repo_commit_section.vue
@@ -127,7 +127,7 @@ export default {
           <button
             v-if="!discardDraftButtonDisabled"
             type="button"
-            class="btn btn-default btn-sm pull-right"
+            class="btn btn-secondary btn-sm pull-right"
             @click="discardDraft"
           >
             {{ __('Discard draft') }}
diff --git a/app/assets/javascripts/issue_show/components/edit_actions.vue b/app/assets/javascripts/issue_show/components/edit_actions.vue
index a539506bce2..cabf4254bf0 100644
--- a/app/assets/javascripts/issue_show/components/edit_actions.vue
+++ b/app/assets/javascripts/issue_show/components/edit_actions.vue
@@ -64,7 +64,7 @@
       </i>
     </button>
     <button
-      class="btn btn-default pull-right"
+      class="btn btn-secondary pull-right"
       type="button"
       @click="closeForm">
       Cancel
diff --git a/app/assets/javascripts/issue_show/components/title.vue b/app/assets/javascripts/issue_show/components/title.vue
index aec890a2ff6..faaeaab2f35 100644
--- a/app/assets/javascripts/issue_show/components/title.vue
+++ b/app/assets/javascripts/issue_show/components/title.vue
@@ -79,7 +79,7 @@
       v-tooltip
       v-if="showInlineEditButton && canUpdate"
       type="button"
-      class="btn btn-default btn-edit btn-svg js-issuable-edit"
+      class="btn btn-secondary btn-edit btn-svg js-issuable-edit"
       v-html="pencilIcon"
       title="Edit title and description"
       data-placement="bottom"
diff --git a/app/assets/javascripts/jobs/components/sidebar_details_block.vue b/app/assets/javascripts/jobs/components/sidebar_details_block.vue
index af47056d98f..191286a2c53 100644
--- a/app/assets/javascripts/jobs/components/sidebar_details_block.vue
+++ b/app/assets/javascripts/jobs/components/sidebar_details_block.vue
@@ -173,7 +173,7 @@
           class="btn-group prepend-top-5"
           role="group">
           <a
-            class="js-cancel-job btn btn-sm btn-default"
+            class="js-cancel-job btn btn-sm btn-secondary"
             :href="job.cancel_path"
             data-method="post"
             rel="nofollow"
diff --git a/app/assets/javascripts/notes/components/diff_file_header.vue b/app/assets/javascripts/notes/components/diff_file_header.vue
index 94d9dc69964..492c4804928 100644
--- a/app/assets/javascripts/notes/components/diff_file_header.vue
+++ b/app/assets/javascripts/notes/components/diff_file_header.vue
@@ -35,7 +35,7 @@ export default {
         <clipboard-button
           title="Copy file path to clipboard"
           :text="diffFile.submoduleLink"
-          css-class="btn-default btn-transparent btn-clipboard"
+          css-class="btn-secondary btn-transparent btn-clipboard"
         />
       </span>
     </div>
@@ -80,7 +80,7 @@ export default {
       <clipboard-button
         title="Copy file path to clipboard"
         :text="diffFile.filePath"
-        css-class="btn-default btn-transparent btn-clipboard"
+        css-class="btn-secondary btn-transparent btn-clipboard"
       />
 
       <small
diff --git a/app/assets/javascripts/notes/components/discussion_counter.vue b/app/assets/javascripts/notes/components/discussion_counter.vue
index d492d1cd001..a75af1e5322 100644
--- a/app/assets/javascripts/notes/components/discussion_counter.vue
+++ b/app/assets/javascripts/notes/components/discussion_counter.vue
@@ -99,7 +99,7 @@ export default {
           v-tooltip
           title="Resolve all discussions in new issue"
           data-container="body"
-          class="new-issue-for-discussion btn btn-default discussion-create-issue-btn">
+          class="new-issue-for-discussion btn btn-secondary discussion-create-issue-btn">
           <span v-html="mrIssueSvg"></span>
         </a>
       </div>
@@ -112,7 +112,7 @@ export default {
           v-tooltip
           title="Jump to first unresolved discussion"
           data-container="body"
-          class="btn btn-default discussion-next-btn">
+          class="btn btn-secondary discussion-next-btn">
           <span v-html="nextDiscussionSvg"></span>
         </button>
       </div>
diff --git a/app/assets/javascripts/notes/components/note_form.vue b/app/assets/javascripts/notes/components/note_form.vue
index c59a2e7a406..d03743a1b63 100644
--- a/app/assets/javascripts/notes/components/note_form.vue
+++ b/app/assets/javascripts/notes/components/note_form.vue
@@ -191,7 +191,7 @@ js-autosize markdown-area js-vue-issue-note-form js-vue-textarea"
         <button
           v-if="note.resolvable"
           @click.prevent="handleUpdate(true)"
-          class="btn btn-nr btn-default append-right-10 js-comment-resolve-button"
+          class="btn btn-nr btn-secondary append-right-10 js-comment-resolve-button"
         >
           {{ resolveButtonTitle }}
         </button>
diff --git a/app/assets/javascripts/notes/components/noteable_discussion.vue b/app/assets/javascripts/notes/components/noteable_discussion.vue
index 476b15aca4a..aa166a056e4 100644
--- a/app/assets/javascripts/notes/components/noteable_discussion.vue
+++ b/app/assets/javascripts/notes/components/noteable_discussion.vue
@@ -279,7 +279,7 @@ Please check your network connection and try again.`;
                         <button
                           @click="resolveHandler()"
                           type="button"
-                          class="btn btn-default"
+                          class="btn btn-secondary"
                         >
                           <i
                             v-if="isResolving"
@@ -302,7 +302,7 @@ Please check your network connection and try again.`;
                             :href="note.resolve_with_issue_path"
                             v-tooltip
                             class="new-issue-for-discussion btn
-                              btn-default discussion-create-issue-btn"
+                              btn-secondary discussion-create-issue-btn"
                             title="Resolve this discussion in a new issue"
                             data-container="body"
                           >
@@ -316,7 +316,7 @@ Please check your network connection and try again.`;
                           <button
                             @click="jumpToDiscussion"
                             v-tooltip
-                            class="btn btn-default discussion-next-btn"
+                            class="btn btn-secondary discussion-next-btn"
                             title="Jump to next unresolved discussion"
                             data-container="body"
                           >
diff --git a/app/assets/javascripts/pages/projects/pipeline_schedules/shared/components/pipeline_schedules_callout.vue b/app/assets/javascripts/pages/projects/pipeline_schedules/shared/components/pipeline_schedules_callout.vue
index 77508e62cef..5edbec08975 100644
--- a/app/assets/javascripts/pages/projects/pipeline_schedules/shared/components/pipeline_schedules_callout.vue
+++ b/app/assets/javascripts/pages/projects/pipeline_schedules/shared/components/pipeline_schedules_callout.vue
@@ -34,7 +34,7 @@
     <div class="bordered-box landing content-block">
       <button
         id="dismiss-callout-btn"
-        class="btn btn-default close"
+        class="btn btn-secondary close"
         @click="dismissCallout">
         <i
           aria-hidden="true"
diff --git a/app/assets/javascripts/pipelines/components/nav_controls.vue b/app/assets/javascripts/pipelines/components/nav_controls.vue
index eba5678e3e5..944c3fbefbc 100644
--- a/app/assets/javascripts/pipelines/components/nav_controls.vue
+++ b/app/assets/javascripts/pipelines/components/nav_controls.vue
@@ -52,14 +52,14 @@
       v-if="resetCachePath"
       @click="onClickResetCache"
       :loading="isResetCacheButtonLoading"
-      class="btn btn-default js-clear-cache"
+      class="btn btn-secondary js-clear-cache"
       :label="s__('Pipelines|Clear Runner Caches')"
     />
 
     <a
       v-if="ciLintPath"
       :href="ciLintPath"
-      class="btn btn-default js-ci-lint"
+      class="btn btn-secondary js-ci-lint"
     >
       {{ s__('Pipelines|CI Lint') }}
     </a>
diff --git a/app/assets/javascripts/pipelines/components/pipelines_actions.vue b/app/assets/javascripts/pipelines/components/pipelines_actions.vue
index 3297af7bde4..eb9956243d5 100644
--- a/app/assets/javascripts/pipelines/components/pipelines_actions.vue
+++ b/app/assets/javascripts/pipelines/components/pipelines_actions.vue
@@ -45,7 +45,7 @@
     <button
       v-tooltip
       type="button"
-      class="dropdown-new btn btn-default js-pipeline-dropdown-manual-actions"
+      class="dropdown-new btn btn-secondary js-pipeline-dropdown-manual-actions"
       title="Manual job"
       data-toggle="dropdown"
       data-placement="top"
diff --git a/app/assets/javascripts/pipelines/components/pipelines_artifacts.vue b/app/assets/javascripts/pipelines/components/pipelines_artifacts.vue
index 1b9e0f917a4..2c82b69d350 100644
--- a/app/assets/javascripts/pipelines/components/pipelines_artifacts.vue
+++ b/app/assets/javascripts/pipelines/components/pipelines_artifacts.vue
@@ -24,7 +24,7 @@
   >
     <button
       v-tooltip
-      class="dropdown-toggle btn btn-default build-artifacts js-pipeline-dropdown-download"
+      class="dropdown-toggle btn btn-secondary build-artifacts js-pipeline-dropdown-download"
       title="Artifacts"
       data-placement="top"
       data-toggle="dropdown"
diff --git a/app/assets/javascripts/pipelines/components/pipelines_table_row.vue b/app/assets/javascripts/pipelines/components/pipelines_table_row.vue
index 4cbd67e0372..5df1e81ab34 100644
--- a/app/assets/javascripts/pipelines/components/pipelines_table_row.vue
+++ b/app/assets/javascripts/pipelines/components/pipelines_table_row.vue
@@ -303,7 +303,7 @@
         <async-button-component
           v-if="pipeline.flags.retryable"
           :endpoint="pipeline.retry_path"
-          css-class="js-pipelines-retry-button btn-default btn-retry"
+          css-class="js-pipelines-retry-button btn-secondary btn-retry"
           title="Retry"
           icon="repeat"
           :pipeline-id="pipeline.id"
diff --git a/app/assets/javascripts/registry/components/collapsible_container.vue b/app/assets/javascripts/registry/components/collapsible_container.vue
index a03180e80e6..f6cb84d24c5 100644
--- a/app/assets/javascripts/registry/components/collapsible_container.vue
+++ b/app/assets/javascripts/registry/components/collapsible_container.vue
@@ -86,7 +86,7 @@
         v-if="repo.location"
         :text="clipboardText"
         :title="repo.location"
-        css-class="btn-default btn-transparent btn-clipboard"
+        css-class="btn-secondary btn-transparent btn-clipboard"
       />
 
       <div class="controls hidden-xs pull-right">
diff --git a/app/assets/javascripts/registry/components/table_registry.vue b/app/assets/javascripts/registry/components/table_registry.vue
index ee4eb3581f3..8afaf9362f8 100644
--- a/app/assets/javascripts/registry/components/table_registry.vue
+++ b/app/assets/javascripts/registry/components/table_registry.vue
@@ -90,7 +90,7 @@
               v-if="item.location"
               :title="item.location"
               :text="clipboardText(item.location)"
-              css-class="btn-default btn-transparent btn-clipboard"
+              css-class="btn-secondary btn-transparent btn-clipboard"
             />
           </td>
           <td>
diff --git a/app/assets/javascripts/sidebar/components/confidential/edit_form_buttons.vue b/app/assets/javascripts/sidebar/components/confidential/edit_form_buttons.vue
index 38b1ddbfd5b..79ebf04fe25 100644
--- a/app/assets/javascripts/sidebar/components/confidential/edit_form_buttons.vue
+++ b/app/assets/javascripts/sidebar/components/confidential/edit_form_buttons.vue
@@ -38,7 +38,7 @@ export default {
   <div class="sidebar-item-warning-message-actions">
     <button
       type="button"
-      class="btn btn-default append-right-10"
+      class="btn btn-secondary append-right-10"
       @click="closeForm"
     >
       {{ __('Cancel') }}
diff --git a/app/assets/javascripts/sidebar/components/lock/edit_form_buttons.vue b/app/assets/javascripts/sidebar/components/lock/edit_form_buttons.vue
index 5e7b8f9698f..2fe4c1d4208 100644
--- a/app/assets/javascripts/sidebar/components/lock/edit_form_buttons.vue
+++ b/app/assets/javascripts/sidebar/components/lock/edit_form_buttons.vue
@@ -42,7 +42,7 @@ export default {
   <div class="sidebar-item-warning-message-actions">
     <button
       type="button"
-      class="btn btn-default append-right-10"
+      class="btn btn-secondary append-right-10"
       @click="closeForm"
     >
       {{ __('Cancel') }}
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/deployment.vue b/app/assets/javascripts/vue_merge_request_widget/components/deployment.vue
index 7bef2e97349..493a430d344 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/deployment.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/deployment.vue
@@ -127,7 +127,7 @@ export default {
           </span>
           <loading-button
             v-if="deployment.stop_url"
-            container-class="btn btn-default btn-xs prepend-left-default"
+            container-class="btn btn-secondary btn-xs prepend-left-default"
             label="Stop environment"
             :loading="isStopping"
             @click="stopEnvironment"
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/mr_widget_header.vue b/app/assets/javascripts/vue_merge_request_widget/components/mr_widget_header.vue
index 18ee4c62bf1..bc8893525c6 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/mr_widget_header.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/mr_widget_header.vue
@@ -71,7 +71,7 @@ export default {
         <clipboard-button
           :text="branchNameClipboardData"
           :title="__('Copy branch name to clipboard')"
-          css-class="btn-default btn-transparent btn-clipboard"
+          css-class="btn-secondary btn-transparent btn-clipboard"
         />
 
         {{ s__("mrWidget|into") }}
@@ -103,7 +103,7 @@ export default {
       <a
         v-if="!mr.sourceBranchRemoved"
         :href="webIdePath"
-        class="btn btn-sm btn-default inline js-web-ide"
+        class="btn btn-sm btn-secondary inline js-web-ide"
       >
         {{ s__("mrWidget|Web IDE") }}
       </a>
@@ -111,7 +111,7 @@ export default {
         data-target="#modal_merge_info"
         data-toggle="modal"
         :disabled="mr.sourceBranchRemoved"
-        class="btn btn-sm btn-default inline js-check-out-branch"
+        class="btn btn-sm btn-secondary inline js-check-out-branch"
         type="button"
       >
         {{ s__("mrWidget|Check out branch") }}
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_auto_merge_failed.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_auto_merge_failed.vue
index ebaf2b972eb..03b736d38b4 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_auto_merge_failed.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_auto_merge_failed.vue
@@ -42,7 +42,7 @@
         @click="refreshWidget"
         :disabled="isRefreshing"
         type="button"
-        class="btn btn-xs btn-default"
+        class="btn btn-xs btn-secondary"
       >
         <loading-icon
           v-if="isRefreshing"
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_conflicts.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_conflicts.vue
index dad4b0fe49d..dd11210570e 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_conflicts.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_conflicts.vue
@@ -43,13 +43,13 @@ To merge this request, first rebase locally.`) }}
         <a
           v-if="mr.canMerge && mr.conflictResolutionPath"
           :href="mr.conflictResolutionPath"
-          class="js-resolve-conflicts-button btn btn-default btn-xs"
+          class="js-resolve-conflicts-button btn btn-secondary btn-xs"
         >
           {{ s__("mrWidget|Resolve conflicts") }}
         </a>
         <button
           v-if="mr.canMerge"
-          class="js-merge-locally-button btn btn-default btn-xs"
+          class="js-merge-locally-button btn btn-secondary btn-xs"
           data-toggle="modal"
           data-target="#modal_merge_info"
         >
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_failed_to_merge.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_failed_to_merge.vue
index 602b68ea572..0148ecec5bd 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_failed_to_merge.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_failed_to_merge.vue
@@ -94,7 +94,7 @@
         </span>
         <button
           @click="refresh"
-          class="btn btn-default btn-xs js-refresh-button"
+          class="btn btn-secondary btn-xs js-refresh-button"
           type="button"
         >
           {{ s__("mrWidget|Refresh now") }}
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merge_when_pipeline_succeeds.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merge_when_pipeline_succeeds.vue
index 7ff7fc7988a..4adb28e15a0 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merge_when_pipeline_succeeds.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merge_when_pipeline_succeeds.vue
@@ -94,7 +94,7 @@
           :disabled="isCancellingAutoMerge"
           role="button"
           href="#"
-          class="btn btn-xs btn-default js-cancel-auto-merge">
+          class="btn btn-xs btn-secondary js-cancel-auto-merge">
           <i
             v-if="isCancellingAutoMerge"
             class="fa fa-spinner fa-spin"
@@ -129,7 +129,7 @@
             :disabled="isRemovingSourceBranch"
             @click.prevent="removeSourceBranch"
             role="button"
-            class="btn btn-xs btn-default js-remove-source-branch"
+            class="btn btn-xs btn-secondary js-remove-source-branch"
             href="#"
           >
             <i
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merged.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merged.vue
index c1618bc6ea0..54044b0cf65 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merged.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merged.vue
@@ -137,7 +137,7 @@
         <a
           v-if="mr.canCherryPickInCurrentMR"
           v-tooltip
-          class="btn btn-default btn-xs"
+          class="btn btn-secondary btn-xs"
           href="#modal-cherry-pick-commit"
           data-toggle="modal"
           data-container="body"
@@ -148,7 +148,7 @@
         <a
           v-else-if="mr.cherryPickInForkPath"
           v-tooltip
-          class="btn btn-default btn-xs"
+          class="btn btn-secondary btn-xs"
           data-method="post"
           :href="mr.cherryPickInForkPath"
           :title="cherryPickTitle"
@@ -175,7 +175,7 @@
             @click="removeSourceBranch"
             :disabled="isMakingRequest"
             type="button"
-            class="btn btn-xs btn-default js-remove-branch-button"
+            class="btn btn-xs btn-secondary js-remove-branch-button"
           >
             {{ s__("mrWidget|Remove Source Branch") }}
           </button>
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/unresolved_discussions.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/unresolved_discussions.vue
index 9ade6a91747..eeead11650f 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/states/unresolved_discussions.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/unresolved_discussions.vue
@@ -25,7 +25,7 @@ export default {
       <a
         v-if="mr.createIssueToResolveDiscussionsPath"
         :href="mr.createIssueToResolveDiscussionsPath"
-        class="btn btn-default btn-xs js-create-issue">
+        class="btn btn-secondary btn-xs js-create-issue">
         Create an issue to resolve them later
       </a>
     </div>
diff --git a/app/assets/javascripts/vue_shared/components/clipboard_button.vue b/app/assets/javascripts/vue_shared/components/clipboard_button.vue
index cab126a7eca..01e54c87ad1 100644
--- a/app/assets/javascripts/vue_shared/components/clipboard_button.vue
+++ b/app/assets/javascripts/vue_shared/components/clipboard_button.vue
@@ -31,7 +31,7 @@
       cssClass: {
         type: String,
         required: false,
-        default: 'btn-default',
+        default: 'btn-secondary',
       },
     },
   };
diff --git a/app/assets/javascripts/vue_shared/components/header_ci_component.vue b/app/assets/javascripts/vue_shared/components/header_ci_component.vue
index a0cd0cbd200..3a8e72fb9b4 100644
--- a/app/assets/javascripts/vue_shared/components/header_ci_component.vue
+++ b/app/assets/javascripts/vue_shared/components/header_ci_component.vue
@@ -163,7 +163,7 @@
       <button
         v-if="hasSidebarButton"
         type="button"
-        class="btn btn-default visible-xs-block
+        class="btn btn-secondary visible-xs-block
 visible-sm-block sidebar-toggle-btn js-sidebar-build-toggle js-sidebar-build-toggle-header"
         aria-label="Toggle Sidebar"
         id="toggleSidebar"
diff --git a/app/assets/javascripts/vue_shared/components/markdown/toolbar.vue b/app/assets/javascripts/vue_shared/components/markdown/toolbar.vue
index c0ee88bbf72..62552839f8d 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/toolbar.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/toolbar.vue
@@ -111,7 +111,7 @@
         Attach a file
       </button>
       <button
-        class="btn btn-default btn-xs hide button-cancel-uploading-files"
+        class="btn btn-secondary btn-xs hide button-cancel-uploading-files"
         type="button"
       >
         Cancel
diff --git a/app/assets/javascripts/vue_shared/components/sidebar/labels_select/dropdown_create_label.vue b/app/assets/javascripts/vue_shared/components/sidebar/labels_select/dropdown_create_label.vue
index 34a07f33a23..bf4fdf31299 100644
--- a/app/assets/javascripts/vue_shared/components/sidebar/labels_select/dropdown_create_label.vue
+++ b/app/assets/javascripts/vue_shared/components/sidebar/labels_select/dropdown_create_label.vue
@@ -83,7 +83,7 @@ export default {
         </button>
         <button
           type="button"
-          class="btn btn-default pull-right js-cancel-label-btn"
+          class="btn btn-secondary pull-right js-cancel-label-btn"
         >
           {{ __('Cancel') }}
         </button>
diff --git a/app/views/admin/conversational_development_index/_callout.html.haml b/app/views/admin/conversational_development_index/_callout.html.haml
index 33a4dab1e00..9f7e0463a91 100644
--- a/app/views/admin/conversational_development_index/_callout.html.haml
+++ b/app/views/admin/conversational_development_index/_callout.html.haml
@@ -1,7 +1,7 @@
 .prepend-top-default
 .user-callout{ data: { uid: 'convdev_intro_callout_dismissed' } }
   .bordered-box.landing.content-block
-    %button.btn.btn-default.close.js-close-callout{ type: 'button',
+    %button.btn.btn-secondary.close.js-close-callout{ type: 'button',
       'aria-label' => 'Dismiss ConvDev introduction' }
       = icon('times', class: 'dismiss-icon', 'aria-hidden' => 'true')
     .user-callout-copy
diff --git a/app/views/admin/health_check/_failing_storages.html.haml b/app/views/admin/health_check/_failing_storages.html.haml
index 6830201538d..d60102b65ea 100644
--- a/app/views/admin/health_check/_failing_storages.html.haml
+++ b/app/views/admin/health_check/_failing_storages.html.haml
@@ -12,4 +12,4 @@
   = _("Access to failing storages has been temporarily disabled to allow the mount to recover. Reset storage information after the issue has been resolved to allow access again.")
   .prepend-top-10
     = button_to _("Reset git storage health information"), reset_storage_health_admin_health_check_path,
-      method: :post, class: 'btn btn-default'
+      method: :post, class: 'btn btn-secondary'
diff --git a/app/views/admin/health_check/show.html.haml b/app/views/admin/health_check/show.html.haml
index e31fb58b205..d9617f88347 100644
--- a/app/views/admin/health_check/show.html.haml
+++ b/app/views/admin/health_check/show.html.haml
@@ -11,7 +11,7 @@
     %code#health-check-token= Gitlab::CurrentSettings.health_check_access_token
     .prepend-top-10
       = button_to _("Reset health check access token"), reset_health_check_token_admin_application_settings_path,
-        method: :put, class: 'btn btn-default',
+        method: :put, class: 'btn btn-secondary',
         data: { confirm: _('Are you sure you want to reset the health check token?') }
   %p.light
     #{ _('Health information can be retrieved from the following endpoints. More information is available') }
diff --git a/app/views/admin/hook_logs/show.html.haml b/app/views/admin/hook_logs/show.html.haml
index 56127bacda2..0caccc809bd 100644
--- a/app/views/admin/hook_logs/show.html.haml
+++ b/app/views/admin/hook_logs/show.html.haml
@@ -4,7 +4,7 @@
 
 %hr
 
-= link_to 'Resend Request', retry_admin_hook_hook_log_path(@hook, @hook_log), class: "btn btn-default pull-right prepend-left-10"
+= link_to 'Resend Request', retry_admin_hook_hook_log_path(@hook, @hook_log), class: "btn btn-secondary pull-right prepend-left-10"
 
 = render partial: 'shared/hook_logs/content', locals: { hook_log: @hook_log }
 
diff --git a/app/views/admin/runners/_runner.html.haml b/app/views/admin/runners/_runner.html.haml
index e1cee584929..c5a0248def6 100644
--- a/app/views/admin/runners/_runner.html.haml
+++ b/app/views/admin/runners/_runner.html.haml
@@ -36,14 +36,14 @@
       Never
   %td.admin-runner-btn-group-cell
     .pull-right.btn-group
-      = link_to admin_runner_path(runner), class: 'btn btn-sm btn-default has-tooltip', title: 'Edit', ref: 'tooltip', aria: { label: 'Edit' }, data: { placement: 'top', container: 'body'} do
+      = link_to admin_runner_path(runner), class: 'btn btn-sm btn-secondary has-tooltip', title: 'Edit', ref: 'tooltip', aria: { label: 'Edit' }, data: { placement: 'top', container: 'body'} do
         = icon('pencil')
       &nbsp;
       - if runner.active?
-        = link_to [:pause, :admin, runner], method: :get, class: 'btn btn-sm btn-default has-tooltip', title: 'Pause', ref: 'tooltip', aria: { label: 'Pause' }, data: { placement: 'top', container: 'body', confirm: "Are you sure?" } do
+        = link_to [:pause, :admin, runner], method: :get, class: 'btn btn-sm btn-secondary has-tooltip', title: 'Pause', ref: 'tooltip', aria: { label: 'Pause' }, data: { placement: 'top', container: 'body', confirm: "Are you sure?" } do
           = icon('pause')
       - else
-        = link_to [:resume, :admin, runner], method: :get, class: 'btn btn-default btn-sm has-tooltip', title: 'Resume', ref: 'tooltip', aria: { label: 'Resume' }, data: { placement: 'top', container: 'body'} do
+        = link_to [:resume, :admin, runner], method: :get, class: 'btn btn-secondary btn-sm has-tooltip', title: 'Resume', ref: 'tooltip', aria: { label: 'Resume' }, data: { placement: 'top', container: 'body'} do
           = icon('play')
       = link_to [:admin, runner], method: :delete, class: 'btn btn-danger btn-sm has-tooltip', title: 'Remove', ref: 'tooltip', aria: { label: 'Remove' }, data: { placement: 'top', container: 'body', confirm: "Are you sure?" } do
         = icon('remove')
diff --git a/app/views/admin/runners/index.html.haml b/app/views/admin/runners/index.html.haml
index 9f13dbbbd82..806be58acb2 100644
--- a/app/views/admin/runners/index.html.haml
+++ b/app/views/admin/runners/index.html.haml
@@ -32,7 +32,7 @@
         You can reset runners registration token by pressing a button below.
       .prepend-top-10
         = button_to _("Reset runners registration token"), reset_runners_token_admin_application_settings_path,
-          method: :put, class: 'btn btn-default',
+          method: :put, class: 'btn btn-secondary',
           data: { confirm: _("Are you sure you want to reset registration token?") }
 
   = render partial: 'ci/runner/how_to_setup_shared_runner',
diff --git a/app/views/admin/users/_user.html.haml b/app/views/admin/users/_user.html.haml
index bbfeceff5b9..0e9d236660c 100644
--- a/app/views/admin/users/_user.html.haml
+++ b/app/views/admin/users/_user.html.haml
@@ -18,7 +18,7 @@
     = link_to 'Edit', edit_admin_user_path(user), id: "edit_#{dom_id(user)}", class: 'btn'
     - unless user == current_user
       .dropdown.inline
-        %a.dropdown-new.btn.btn-default#project-settings-button{ href: '#', data: { toggle: 'dropdown' } }
+        %a.dropdown-new.btn.btn-secondary#project-settings-button{ href: '#', data: { toggle: 'dropdown' } }
           = icon('cog')
           = icon('caret-down')
         %ul.dropdown-menu.dropdown-menu-align-right
diff --git a/app/views/discussions/_jump_to_next.html.haml b/app/views/discussions/_jump_to_next.html.haml
index 3db509f24a5..e3bb113768f 100644
--- a/app/views/discussions/_jump_to_next.html.haml
+++ b/app/views/discussions/_jump_to_next.html.haml
@@ -2,7 +2,7 @@
 - if current_user
   %jump-to-discussion{ "inline-template" => true, ":discussion-id" => "'#{discussion.try(:id)}'" }
     .btn-group{ role: "group", "v-show" => "!allResolved", "v-if" => "showButton" }
-      %button.btn.btn-default.discussion-next-btn.has-tooltip{ "@click" => "jumpToNextUnresolvedDiscussion",
+      %button.btn.btn-secondary.discussion-next-btn.has-tooltip{ "@click" => "jumpToNextUnresolvedDiscussion",
         ":title" => "buttonText",
         ":aria-label" => "buttonText",
         data: { container: "body" } }
diff --git a/app/views/discussions/_new_issue_for_all_discussions.html.haml b/app/views/discussions/_new_issue_for_all_discussions.html.haml
index 50dd5864195..74f52a4e312 100644
--- a/app/views/discussions/_new_issue_for_all_discussions.html.haml
+++ b/app/views/discussions/_new_issue_for_all_discussions.html.haml
@@ -5,4 +5,4 @@
               title: 'Resolve all discussions in new issue',
               aria: { label: 'Resolve all discussions in new issue' },
               data: { container: 'body' },
-              class: 'new-issue-for-discussion btn btn-default discussion-create-issue-btn has-tooltip'
+              class: 'new-issue-for-discussion btn btn-secondary discussion-create-issue-btn has-tooltip'
diff --git a/app/views/discussions/_new_issue_for_discussion.html.haml b/app/views/discussions/_new_issue_for_discussion.html.haml
index 2bfe118c608..9969fa68270 100644
--- a/app/views/discussions/_new_issue_for_discussion.html.haml
+++ b/app/views/discussions/_new_issue_for_discussion.html.haml
@@ -7,4 +7,4 @@
                 title: 'Resolve this discussion in a new issue',
                 aria: { label: 'Resolve this discussion in a new issue' },
                 data: { container: 'body' },
-                class: 'new-issue-for-discussion btn btn-default discussion-create-issue-btn has-tooltip'
+                class: 'new-issue-for-discussion btn btn-secondary discussion-create-issue-btn has-tooltip'
diff --git a/app/views/discussions/_resolve_all.html.haml b/app/views/discussions/_resolve_all.html.haml
index 689a22acd27..ad55ca25bfb 100644
--- a/app/views/discussions/_resolve_all.html.haml
+++ b/app/views/discussions/_resolve_all.html.haml
@@ -3,6 +3,6 @@
     ":can-resolve" => discussion.can_resolve?(current_user),
     "inline-template" => true }
   .btn-group{ role: "group", "v-if" => "showButton" }
-    %button.btn.btn-default{ type: "button", "@click" => "resolve", ":disabled" => "loading", "v-cloak" => "true" }
+    %button.btn.btn-secondary{ type: "button", "@click" => "resolve", ":disabled" => "loading", "v-cloak" => "true" }
       = icon("spinner spin", "v-show" => "loading")
       {{ buttonText }}
diff --git a/app/views/help/ui.html.haml b/app/views/help/ui.html.haml
index ce09b44fbb2..c33100c4f84 100644
--- a/app/views/help/ui.html.haml
+++ b/app/views/help/ui.html.haml
@@ -205,7 +205,7 @@
   %h2#buttons Buttons
 
   .example
-    %button.btn.btn-default{ :type => "button" } Default
+    %button.btn.btn-secondary{ :type => "button" } Default
     %button.btn.btn-gray{ :type => "button" } Gray
     %button.btn.btn-primary{ :type => "button" } Primary
     %button.btn.btn-success{ :type => "button" } Success
@@ -478,7 +478,7 @@
               Remember me
       .form-group
         .col-sm-offset-2.col-sm-10
-          %button.btn.btn-default{ :type => "submit" } Sign in
+          %button.btn.btn-secondary{ :type => "submit" } Sign in
 
   .lead
     Form when label rendered above input
@@ -496,7 +496,7 @@
         %label
           %input{ :type => "checkbox" }/
           Remember me
-      %button.btn.btn-default{ :type => "submit" } Sign in
+      %button.btn.btn-secondary{ :type => "submit" } Sign in
 
   %h2#file File
   %h4
diff --git a/app/views/projects/_export.html.haml b/app/views/projects/_export.html.haml
index 1e7d9444986..6f49cac9a49 100644
--- a/app/views/projects/_export.html.haml
+++ b/app/views/projects/_export.html.haml
@@ -33,9 +33,9 @@
       Once the exported file is ready, you will receive a notification email with a download link, or you can download it from this page.
     - if project.export_project_path
       = link_to 'Download export',  download_export_project_path(project),
-              rel: 'nofollow', download: '', method: :get, class: "btn btn-default"
+              rel: 'nofollow', download: '', method: :get, class: "btn btn-secondary"
       = link_to 'Generate new export',  generate_new_export_project_path(project),
-              method: :post, class: "btn btn-default"
+              method: :post, class: "btn btn-secondary"
     - else
       = link_to 'Export project', export_project_path(project),
-              method: :post, class: "btn btn-default"
+              method: :post, class: "btn btn-secondary"
diff --git a/app/views/projects/_project_templates.html.haml b/app/views/projects/_project_templates.html.haml
index d50175727be..41ca5614d31 100644
--- a/app/views/projects/_project_templates.html.haml
+++ b/app/views/projects/_project_templates.html.haml
@@ -7,7 +7,7 @@
       %label.btn.btn-success.template-button.choose-template.append-right-10{ for: template.name }
         %input{ type: "radio",  autocomplete: "off", name: "project[template_name]", id: template.name, value: template.name }
         %span Use template
-      %a.btn.btn-default{ href: template.preview, rel: 'noopener noreferrer', target: '_blank' } Preview
+      %a.btn.btn-secondary{ href: template.preview, rel: 'noopener noreferrer', target: '_blank' } Preview
 
   .project-fields-form
     .form-group
@@ -19,6 +19,6 @@
             - Gitlab::ProjectTemplate.all.each do |template|
               = custom_icon(template.logo)
           .selected-template
-        %button.btn.btn-default.change-template{ type: "button" } Change template
+        %button.btn.btn-secondary.change-template{ type: "button" } Change template
 
     = render 'new_project_fields', f: f, project_name_id: "template-project-name"
diff --git a/app/views/projects/artifacts/browse.html.haml b/app/views/projects/artifacts/browse.html.haml
index 7ff7466e561..42b2abc42f1 100644
--- a/app/views/projects/artifacts/browse.html.haml
+++ b/app/views/projects/artifacts/browse.html.haml
@@ -17,7 +17,7 @@
 
     .tree-controls
       = link_to download_project_job_artifacts_path(@project, @build),
-        rel: 'nofollow', download: '', class: 'btn btn-default download' do
+        rel: 'nofollow', download: '', class: 'btn btn-secondary download' do
         = sprite_icon('download')
         Download artifacts archive
 
diff --git a/app/views/projects/blob/_viewer_switcher.html.haml b/app/views/projects/blob/_viewer_switcher.html.haml
index 6a521069418..b1ce9499727 100644
--- a/app/views/projects/blob/_viewer_switcher.html.haml
+++ b/app/views/projects/blob/_viewer_switcher.html.haml
@@ -4,9 +4,9 @@
 
   .btn-group.js-blob-viewer-switcher{ role: "group" }
     - simple_label = "Display #{simple_viewer.switcher_title}"
-    %button.btn.btn-default.btn-sm.js-blob-viewer-switch-btn.has-tooltip{ 'aria-label' => simple_label, title: simple_label, data: { viewer: 'simple', container: 'body' } }>
+    %button.btn.btn-secondary.btn-sm.js-blob-viewer-switch-btn.has-tooltip{ 'aria-label' => simple_label, title: simple_label, data: { viewer: 'simple', container: 'body' } }>
       = icon(simple_viewer.switcher_icon)
 
     - rich_label = "Display #{rich_viewer.switcher_title}"
-    %button.btn.btn-default.btn-sm.js-blob-viewer-switch-btn.has-tooltip{ 'aria-label' => rich_label, title: rich_label, data: { viewer: 'rich', container: 'body' } }>
+    %button.btn.btn-secondary.btn-sm.js-blob-viewer-switch-btn.has-tooltip{ 'aria-label' => rich_label, title: rich_label, data: { viewer: 'rich', container: 'body' } }>
       = icon(rich_viewer.switcher_icon)
diff --git a/app/views/projects/blob/viewers/_stl.html.haml b/app/views/projects/blob/viewers/_stl.html.haml
index 55dd8cba7fe..fd448c2bae7 100644
--- a/app/views/projects/blob/viewers/_stl.html.haml
+++ b/app/views/projects/blob/viewers/_stl.html.haml
@@ -3,7 +3,7 @@
     = icon('spinner spin 2x', class: 'prepend-top-default append-bottom-default', 'aria-hidden' => 'true', 'aria-label' => 'Loading')
   .text-center.prepend-top-default.append-bottom-default.stl-controls
     .btn-group
-      %button.btn.btn-default.btn-sm.js-material-changer{ data: { type: 'wireframe' } }
+      %button.btn.btn-secondary.btn-sm.js-material-changer{ data: { type: 'wireframe' } }
         Wireframe
-      %button.btn.btn-default.btn-sm.active.js-material-changer{ data: { type: 'default' } }
+      %button.btn.btn-secondary.btn-sm.active.js-material-changer{ data: { type: 'default' } }
         Solid
diff --git a/app/views/projects/branches/_branch.html.haml b/app/views/projects/branches/_branch.html.haml
index 883dfb3e6c8..09e5e28f5c4 100644
--- a/app/views/projects/branches/_branch.html.haml
+++ b/app/views/projects/branches/_branch.html.haml
@@ -42,12 +42,12 @@
 
   .controls.hidden-xs<
     - if merge_project && create_mr_button?(@repository.root_ref, branch.name)
-      = link_to create_mr_path(@repository.root_ref, branch.name), class: 'btn btn-default' do
+      = link_to create_mr_path(@repository.root_ref, branch.name), class: 'btn btn-secondary' do
         = _('Merge request')
 
     - if branch.name != @repository.root_ref
       = link_to project_compare_index_path(@project, from: @repository.root_ref, to: branch.name),
-        class: "btn btn-default #{'prepend-left-10' unless merge_project}",
+        class: "btn btn-secondary #{'prepend-left-10' unless merge_project}",
         method: :post,
         title: s_('Branches|Compare') do
         = s_('Branches|Compare')
diff --git a/app/views/projects/buttons/_fork.html.haml b/app/views/projects/buttons/_fork.html.haml
index f880556a9f7..c1eddc1b2e9 100644
--- a/app/views/projects/buttons/_fork.html.haml
+++ b/app/views/projects/buttons/_fork.html.haml
@@ -7,7 +7,7 @@
     - else
       - can_create_fork = current_user.can?(:create_fork)
       = link_to new_project_fork_path(@project),
-          class: "btn btn-default #{'has-tooltip disabled' unless can_create_fork}",
+          class: "btn btn-secondary #{'has-tooltip disabled' unless can_create_fork}",
           title: (_('You have reached your project limit') unless can_create_fork) do
         = custom_icon('icon_fork')
         %span= s_('CreateNewFork|Fork')
diff --git a/app/views/projects/buttons/_star.html.haml b/app/views/projects/buttons/_star.html.haml
index d8b4266143e..c3384b5939f 100644
--- a/app/views/projects/buttons/_star.html.haml
+++ b/app/views/projects/buttons/_star.html.haml
@@ -1,5 +1,5 @@
 - if current_user
-  %button.btn.btn-default.star-btn.toggle-star{ type: "button", data: { endpoint: toggle_star_project_path(@project, :json) } }
+  %button.btn.btn-secondary.star-btn.toggle-star{ type: "button", data: { endpoint: toggle_star_project_path(@project, :json) } }
     - if current_user.starred?(@project)
       = sprite_icon('star')
       %span.starred= _('Unstar')
diff --git a/app/views/projects/ci/lints/show.html.haml b/app/views/projects/ci/lints/show.html.haml
index 6ca8152183d..f1919ef211d 100644
--- a/app/views/projects/ci/lints/show.html.haml
+++ b/app/views/projects/ci/lints/show.html.haml
@@ -19,7 +19,7 @@
         .pull-left.prepend-top-10
           = submit_tag('Validate', class: 'btn btn-success submit-yml')
         .pull-right.prepend-top-10
-          = button_tag('Clear', type: 'button', class: 'btn btn-default clear-yml')
+          = button_tag('Clear', type: 'button', class: 'btn btn-secondary clear-yml')
 
   .row.prepend-top-20
     .col-sm-12
diff --git a/app/views/projects/clusters/gcp/_show.html.haml b/app/views/projects/clusters/gcp/_show.html.haml
index 78cd687ef93..a7ecb43e3c2 100644
--- a/app/views/projects/clusters/gcp/_show.html.haml
+++ b/app/views/projects/clusters/gcp/_show.html.haml
@@ -4,7 +4,7 @@
   .input-group
     %input.form-control.cluster-name.js-select-on-focus{ value: @cluster.name, readonly: true }
     %span.input-group-btn
-      = clipboard_button(text: @cluster.name, title: s_('ClusterIntegration|Copy Kubernetes cluster name'), class: 'btn-default')
+      = clipboard_button(text: @cluster.name, title: s_('ClusterIntegration|Copy Kubernetes cluster name'), class: 'btn-secondary')
 
 = form_for @cluster, url: namespace_project_cluster_path(@project.namespace, @project, @cluster), as: :cluster do |field|
   = form_errors(@cluster)
@@ -15,7 +15,7 @@
       .input-group
         = platform_kubernetes_field.text_field :api_url, class: 'form-control js-select-on-focus', placeholder: s_('ClusterIntegration|API URL'), readonly: true
         %span.input-group-btn
-          = clipboard_button(text: @cluster.platform_kubernetes.api_url, title: s_('ClusterIntegration|Copy API URL'), class: 'btn-default')
+          = clipboard_button(text: @cluster.platform_kubernetes.api_url, title: s_('ClusterIntegration|Copy API URL'), class: 'btn-secondary')
 
     .form-group
       = platform_kubernetes_field.label :ca_cert, s_('ClusterIntegration|CA Certificate')
@@ -29,9 +29,9 @@
       .input-group
         = platform_kubernetes_field.text_field :token, class: 'form-control js-cluster-token js-select-on-focus', type: 'password', placeholder: s_('ClusterIntegration|Token'), readonly: true
         %span.input-group-btn
-          %button.btn.btn-default.js-show-cluster-token{ type: 'button' }
+          %button.btn.btn-secondary.js-show-cluster-token{ type: 'button' }
             = s_('ClusterIntegration|Show')
-          = clipboard_button(text: @cluster.platform_kubernetes.token, title: s_('ClusterIntegration|Copy Token'), class: 'btn-default')
+          = clipboard_button(text: @cluster.platform_kubernetes.token, title: s_('ClusterIntegration|Copy Token'), class: 'btn-secondary')
 
     .form-group
       = platform_kubernetes_field.label :namespace, s_('ClusterIntegration|Project namespace (optional, unique)')
diff --git a/app/views/projects/commit/_commit_box.html.haml b/app/views/projects/commit/_commit_box.html.haml
index 74c5317428c..e359e7bea6d 100644
--- a/app/views/projects/commit/_commit_box.html.haml
+++ b/app/views/projects/commit/_commit_box.html.haml
@@ -22,10 +22,10 @@
       %span.btn.disabled.btn-grouped.hidden-xs.append-right-10
         = icon('comment')
         = @notes_count
-    = link_to project_tree_path(@project, @commit), class: "btn btn-default append-right-10 hidden-xs hidden-sm" do
+    = link_to project_tree_path(@project, @commit), class: "btn btn-secondary append-right-10 hidden-xs hidden-sm" do
       #{ _('Browse files') }
     .dropdown.inline
-      %a.btn.btn-default.dropdown-toggle{ data: { toggle: "dropdown" } }
+      %a.btn.btn-secondary.dropdown-toggle{ data: { toggle: "dropdown" } }
         %span= _('Options')
         = icon('caret-down')
       %ul.dropdown-menu.dropdown-menu-align-right
diff --git a/app/views/projects/commits/_commit.html.haml b/app/views/projects/commits/_commit.html.haml
index 078bd0eee63..d07222aa455 100644
--- a/app/views/projects/commits/_commit.html.haml
+++ b/app/views/projects/commits/_commit.html.haml
@@ -57,4 +57,4 @@
         = link_to_browse_code(project, commit)
 
         - if view_details && merge_request
-          = link_to "View details", project_commit_path(project, commit.id, merge_request_iid: merge_request.iid), class: "btn btn-default"
+          = link_to "View details", project_commit_path(project, commit.id, merge_request_iid: merge_request.iid), class: "btn btn-secondary"
diff --git a/app/views/projects/deployments/_actions.haml b/app/views/projects/deployments/_actions.haml
index e2baaa625ae..c2dac233684 100644
--- a/app/views/projects/deployments/_actions.haml
+++ b/app/views/projects/deployments/_actions.haml
@@ -3,7 +3,7 @@
   - if actions.present?
     .btn-group
       .dropdown
-        %button.dropdown.dropdown-new.btn.btn-default{ type: 'button', 'data-toggle' => 'dropdown' }
+        %button.dropdown.dropdown-new.btn.btn-secondary{ type: 'button', 'data-toggle' => 'dropdown' }
           = custom_icon('icon_play')
           = icon('caret-down')
         %ul.dropdown-menu.dropdown-menu-align-right
diff --git a/app/views/projects/diffs/_diffs.html.haml b/app/views/projects/diffs/_diffs.html.haml
index 376f672f424..51484a7016f 100644
--- a/app/views/projects/diffs/_diffs.html.haml
+++ b/app/views/projects/diffs/_diffs.html.haml
@@ -8,7 +8,7 @@
   .files-changed-inner
     .inline-parallel-buttons.hidden-xs.hidden-sm
       - if !diffs_expanded? && diff_files.any? { |diff_file| diff_file.collapsed? }
-        = link_to 'Expand all', url_for(params.merge(expanded: 1, format: nil)), class: 'btn btn-default'
+        = link_to 'Expand all', url_for(params.merge(expanded: 1, format: nil)), class: 'btn btn-secondary'
       - if show_whitespace_toggle
         - if current_controller?(:commit)
           = commit_diff_whitespace_link(diffs.project, @commit, class: 'hidden-xs')
diff --git a/app/views/projects/edit.html.haml b/app/views/projects/edit.html.haml
index 99eeb9551e3..7d495003dc3 100644
--- a/app/views/projects/edit.html.haml
+++ b/app/views/projects/edit.html.haml
@@ -104,7 +104,7 @@
         %p
           Runs a number of housekeeping tasks within the current repository, such as compressing file revisions and removing unreachable objects.
         = link_to 'Run housekeeping', housekeeping_project_path(@project),
-            method: :post, class: "btn btn-default"
+            method: :post, class: "btn btn-secondary"
       - if can? current_user, :archive_project, @project
         .sub-section
           %h4.warning-title
diff --git a/app/views/projects/environments/terminal.html.haml b/app/views/projects/environments/terminal.html.haml
index 6ec4ff56552..0cf7b2d01d4 100644
--- a/app/views/projects/environments/terminal.html.haml
+++ b/app/views/projects/environments/terminal.html.haml
@@ -15,7 +15,7 @@
       .col-sm-6
         .nav-controls
           - if @environment.external_url.present?
-            = link_to @environment.external_url, class: 'btn btn-default', target: '_blank', rel: 'noopener noreferrer nofollow' do
+            = link_to @environment.external_url, class: 'btn btn-secondary', target: '_blank', rel: 'noopener noreferrer nofollow' do
               = icon('external-link')
           = render 'projects/deployments/actions', deployment: @environment.last_deployment
 
diff --git a/app/views/projects/hook_logs/show.html.haml b/app/views/projects/hook_logs/show.html.haml
index 1cf4105bd27..bb85980a474 100644
--- a/app/views/projects/hook_logs/show.html.haml
+++ b/app/views/projects/hook_logs/show.html.haml
@@ -4,6 +4,6 @@
       Request details
   .col-lg-9
 
-    = link_to 'Resend Request', retry_project_hook_hook_log_path(@project, @hook, @hook_log), class: "btn btn-default pull-right prepend-left-10"
+    = link_to 'Resend Request', retry_project_hook_hook_log_path(@project, @hook, @hook_log), class: "btn btn-secondary pull-right prepend-left-10"
 
     = render partial: 'shared/hook_logs/content', locals: { hook_log: @hook_log }
diff --git a/app/views/projects/issues/_nav_btns.html.haml b/app/views/projects/issues/_nav_btns.html.haml
index 0d39edb7bfd..0a37f2ae02f 100644
--- a/app/views/projects/issues/_nav_btns.html.haml
+++ b/app/views/projects/issues/_nav_btns.html.haml
@@ -1,7 +1,7 @@
-= link_to params.merge(rss_url_options), class: 'btn btn-default append-right-10 has-tooltip', title: 'Subscribe' do
+= link_to params.merge(rss_url_options), class: 'btn btn-secondary append-right-10 has-tooltip', title: 'Subscribe' do
   = icon('rss')
 - if @can_bulk_update
-  = button_tag "Edit issues", class: "btn btn-default append-right-10 js-bulk-update-toggle"
+  = button_tag "Edit issues", class: "btn btn-secondary append-right-10 js-bulk-update-toggle"
 = link_to "New issue", new_project_issue_path(@project,
                                               issue: { assignee_id: finder.assignee.try(:id),
                                                        milestone_id: finder.milestones.first.try(:id) }),
diff --git a/app/views/projects/issues/show.html.haml b/app/views/projects/issues/show.html.haml
index ec7e87219f5..320d589a9fc 100644
--- a/app/views/projects/issues/show.html.haml
+++ b/app/views/projects/issues/show.html.haml
@@ -25,12 +25,12 @@
         .issuable-warning-icon.inline= sprite_icon('lock', size: 16, css_class: 'icon')
       = issuable_meta(@issue, @project, "Issue")
 
-    %a.btn.btn-default.pull-right.visible-xs-block.gutter-toggle.issuable-gutter-toggle.js-sidebar-toggle{ href: "#" }
+    %a.btn.btn-secondary.pull-right.visible-xs-block.gutter-toggle.issuable-gutter-toggle.js-sidebar-toggle{ href: "#" }
       = icon('angle-double-left')
 
   .detail-page-header-actions.js-issuable-actions
     .clearfix.issue-btn-group.dropdown
-      %button.btn.btn-default.pull-left.hidden-md.hidden-lg{ type: "button", data: { toggle: "dropdown" } }
+      %button.btn.btn-secondary.pull-left.hidden-md.hidden-lg{ type: "button", data: { toggle: "dropdown" } }
         Options
         = icon('caret-down')
       .dropdown-menu.dropdown-menu-align-right.hidden-lg
diff --git a/app/views/projects/jobs/_header.html.haml b/app/views/projects/jobs/_header.html.haml
index 83a2af1dc74..2e975e2163b 100644
--- a/app/views/projects/jobs/_header.html.haml
+++ b/app/views/projects/jobs/_header.html.haml
@@ -27,5 +27,5 @@
         = link_to "New issue", new_project_issue_path(@project, issue: build_failed_issue_options), class: 'btn btn-new btn-inverted'
       - if can?(current_user, :update_build, @build) && @build.retryable?
         = link_to "Retry job", retry_project_job_path(@project, @build), class: 'btn btn-inverted-secondary', method: :post
-    %button.btn.btn-default.pull-right.visible-xs-block.visible-sm-block.build-gutter-toggle.js-sidebar-build-toggle{ role: "button", type: "button" }
+    %button.btn.btn-secondary.pull-right.visible-xs-block.visible-sm-block.build-gutter-toggle.js-sidebar-build-toggle{ role: "button", type: "button" }
       = icon('angle-double-left')
diff --git a/app/views/projects/jobs/_sidebar.html.haml b/app/views/projects/jobs/_sidebar.html.haml
index ecf186e3dc8..f4e54b8a6c8 100644
--- a/app/views/projects/jobs/_sidebar.html.haml
+++ b/app/views/projects/jobs/_sidebar.html.haml
@@ -29,14 +29,14 @@
           - if @build.artifacts?
             .btn-group.btn-group-justified{ role: :group }
               - if @build.has_expiring_artifacts? && can?(current_user, :update_build, @build)
-                = link_to keep_project_job_artifacts_path(@project, @build), class: 'btn btn-sm btn-default', method: :post do
+                = link_to keep_project_job_artifacts_path(@project, @build), class: 'btn btn-sm btn-secondary', method: :post do
                   Keep
 
-              = link_to download_project_job_artifacts_path(@project, @build), rel: 'nofollow', download: '', class: 'btn btn-sm btn-default' do
+              = link_to download_project_job_artifacts_path(@project, @build), rel: 'nofollow', download: '', class: 'btn btn-sm btn-secondary' do
                 Download
 
               - if @build.browsable_artifacts?
-                = link_to browse_project_job_artifacts_path(@project, @build), class: 'btn btn-sm btn-default' do
+                = link_to browse_project_job_artifacts_path(@project, @build), class: 'btn btn-sm btn-secondary' do
                   Browse
 
       - if @build.trigger_request
diff --git a/app/views/projects/jobs/index.html.haml b/app/views/projects/jobs/index.html.haml
index 9963cc93633..1f2750cbca7 100644
--- a/app/views/projects/jobs/index.html.haml
+++ b/app/views/projects/jobs/index.html.haml
@@ -15,7 +15,7 @@
         - unless @repository.gitlab_ci_yml
           = link_to 'Get started with Pipelines', help_page_path('ci/quick_start/README'), class: 'btn btn-info'
 
-        = link_to ci_lint_path, class: 'btn btn-default' do
+        = link_to ci_lint_path, class: 'btn btn-secondary' do
           %span CI lint
 
   .content-list.builds-content-list
diff --git a/app/views/projects/merge_requests/_discussion.html.haml b/app/views/projects/merge_requests/_discussion.html.haml
index 3303aa72604..a57a562d0e5 100644
--- a/app/views/projects/merge_requests/_discussion.html.haml
+++ b/app/views/projects/merge_requests/_discussion.html.haml
@@ -5,7 +5,7 @@
     - if @merge_request.reopenable?
       = link_to 'Reopen merge request', merge_request_path(@merge_request, merge_request: { state_event: :reopen }), method: :put, class: "btn btn-nr btn-comment btn-reopen reopen-mr-link js-note-target-close js-note-target-reopen", title: "Reopen merge request", data: { original_text: "Reopen merge request", alternative_text: "Comment & reopen merge request"}
     %comment-and-resolve-btn{ "inline-template" => true }
-      %button.btn.btn-nr.btn-default.append-right-10.js-comment-resolve-button{ "v-if" => "showButton", type: "submit", data: { project_path: "#{project_path(@merge_request.project)}" } }
+      %button.btn.btn-nr.btn-secondary.append-right-10.js-comment-resolve-button{ "v-if" => "showButton", type: "submit", data: { project_path: "#{project_path(@merge_request.project)}" } }
         {{ buttonText }}
 
 #notes= render "shared/notes/notes_with_form", :autocomplete => true
diff --git a/app/views/projects/merge_requests/_mr_title.html.haml b/app/views/projects/merge_requests/_mr_title.html.haml
index 22c8b6b513d..659e931d8c2 100644
--- a/app/views/projects/merge_requests/_mr_title.html.haml
+++ b/app/views/projects/merge_requests/_mr_title.html.haml
@@ -16,12 +16,12 @@
         .issuable-warning-icon.inline= sprite_icon('lock', size: 16, css_class: 'icon')
       = issuable_meta(@merge_request, @project, "Merge request")
 
-    %a.btn.btn-default.pull-right.visible-xs-block.gutter-toggle.issuable-gutter-toggle.js-sidebar-toggle{ href: "#" }
+    %a.btn.btn-secondary.pull-right.visible-xs-block.gutter-toggle.issuable-gutter-toggle.js-sidebar-toggle{ href: "#" }
       = icon('angle-double-left')
 
   .detail-page-header-actions.js-issuable-actions
     .clearfix.issue-btn-group.dropdown
-      %button.btn.btn-default.pull-left.hidden-md.hidden-lg{ type: "button", data: { toggle: "dropdown" } }
+      %button.btn.btn-secondary.pull-left.hidden-md.hidden-lg{ type: "button", data: { toggle: "dropdown" } }
         Options
         = icon('caret-down')
       .dropdown-menu.dropdown-menu-align-right.hidden-lg
diff --git a/app/views/projects/merge_requests/diffs/_version_controls.html.haml b/app/views/projects/merge_requests/diffs/_version_controls.html.haml
index 1c26f0405d2..726c997d939 100644
--- a/app/views/projects/merge_requests/diffs/_version_controls.html.haml
+++ b/app/views/projects/merge_requests/diffs/_version_controls.html.haml
@@ -3,7 +3,7 @@
     .mr-version-menus-container.content-block
       Changes between
       %span.dropdown.inline.mr-version-dropdown
-        %a.dropdown-toggle.btn.btn-default{ data: {toggle: :dropdown} }
+        %a.dropdown-toggle.btn.btn-secondary{ data: {toggle: :dropdown} }
           %span
             - if @merge_request_diff.latest?
               latest version
@@ -36,7 +36,7 @@
       - if @merge_request_diff.base_commit_sha
         and
         %span.dropdown.inline.mr-version-compare-dropdown
-          %a.btn.btn-default.dropdown-toggle{ data: {toggle: :dropdown} }
+          %a.btn.btn-secondary.dropdown-toggle{ data: {toggle: :dropdown} }
             - if @start_version
               version #{version_index(@start_version)}
             - else
diff --git a/app/views/projects/milestones/show.html.haml b/app/views/projects/milestones/show.html.haml
index 5ec219fdf00..c71728bdd7c 100644
--- a/app/views/projects/milestones/show.html.haml
+++ b/app/views/projects/milestones/show.html.haml
@@ -56,7 +56,7 @@
 
         #delete-milestone-modal
 
-      %a.btn.btn-default.btn-grouped.pull-right.visible-xs-block.js-sidebar-toggle{ href: "#" }
+      %a.btn.btn-secondary.btn-grouped.pull-right.visible-xs-block.js-sidebar-toggle{ href: "#" }
         = icon('angle-double-left')
 
   .detail-page-description.milestone-detail
diff --git a/app/views/projects/project_members/_new_project_member.html.haml b/app/views/projects/project_members/_new_project_member.html.haml
index bf5b11ea30c..e401717180f 100644
--- a/app/views/projects/project_members/_new_project_member.html.haml
+++ b/app/views/projects/project_members/_new_project_member.html.haml
@@ -18,4 +18,4 @@
           = text_field_tag :expires_at, nil, class: 'form-control js-access-expiration-date', placeholder: 'Expiration date'
           %i.clear-icon.js-clear-input
       = f.submit "Add to project", class: "btn btn-create"
-      = link_to "Import", import_project_project_members_path(@project), class: "btn btn-default", title: "Import members from another project"
+      = link_to "Import", import_project_project_members_path(@project), class: "btn btn-secondary", title: "Import members from another project"
diff --git a/app/views/projects/releases/edit.html.haml b/app/views/projects/releases/edit.html.haml
index 4d962f9433f..586eec70f5d 100644
--- a/app/views/projects/releases/edit.html.haml
+++ b/app/views/projects/releases/edit.html.haml
@@ -18,4 +18,4 @@
     .error-alert
     .prepend-top-default
       = f.submit 'Save changes', class: 'btn btn-save'
-      = link_to "Cancel", project_tag_path(@project, @tag.name), class: "btn btn-default btn-cancel"
+      = link_to "Cancel", project_tag_path(@project, @tag.name), class: "btn btn-secondary btn-cancel"
diff --git a/app/views/projects/snippets/_actions.html.haml b/app/views/projects/snippets/_actions.html.haml
index f09871c7fcc..c992856bbb5 100644
--- a/app/views/projects/snippets/_actions.html.haml
+++ b/app/views/projects/snippets/_actions.html.haml
@@ -14,7 +14,7 @@
     = link_to 'Submit as spam', mark_as_spam_project_snippet_path(@project, @snippet), method: :post, class: 'btn btn-grouped btn-spam', title: 'Submit as spam'
 - if can?(current_user, :create_project_snippet, @project) || can?(current_user, :update_project_snippet, @snippet)
   .visible-xs-block.dropdown
-    %button.btn.btn-default.btn-block.append-bottom-0.prepend-top-5{ data: { toggle: "dropdown" } }
+    %button.btn.btn-secondary.btn-block.append-bottom-0.prepend-top-5{ data: { toggle: "dropdown" } }
       Options
       = icon('caret-down')
     .dropdown-menu.dropdown-menu-full-width
diff --git a/app/views/projects/tree/_tree_header.html.haml b/app/views/projects/tree/_tree_header.html.haml
index 5ef5e9c09a2..dea6ea2fb4c 100644
--- a/app/views/projects/tree/_tree_header.html.haml
+++ b/app/views/projects/tree/_tree_header.html.haml
@@ -77,7 +77,7 @@
   = render 'projects/find_file_link'
 
   = succeed " " do
-    = link_to ide_edit_path(@project, @id, ""), class: 'btn btn-default' do
+    = link_to ide_edit_path(@project, @id, ""), class: 'btn btn-secondary' do
       = _('Web IDE')
 
   = render 'projects/buttons/download', project: @project, ref: @ref
diff --git a/app/views/projects/triggers/_trigger.html.haml b/app/views/projects/triggers/_trigger.html.haml
index 6249c32b7cc..cd3ade8368a 100644
--- a/app/views/projects/triggers/_trigger.html.haml
+++ b/app/views/projects/triggers/_trigger.html.haml
@@ -33,10 +33,10 @@
     - take_ownership_confirmation = "By taking ownership you will bind this trigger to your user account. With this the trigger will have access to all your projects as if it was you. Are you sure?"
     - revoke_trigger_confirmation = "By revoking a trigger you will break any processes making use of it. Are you sure?"
     - if trigger.owner != current_user && can?(current_user, :manage_trigger, trigger)
-      = link_to 'Take ownership', take_ownership_project_trigger_path(@project, trigger), data: { confirm: take_ownership_confirmation }, method: :post, class: "btn btn-default btn-sm btn-trigger-take-ownership"
+      = link_to 'Take ownership', take_ownership_project_trigger_path(@project, trigger), data: { confirm: take_ownership_confirmation }, method: :post, class: "btn btn-secondary btn-sm btn-trigger-take-ownership"
     - if can?(current_user, :admin_trigger, trigger)
-      = link_to edit_project_trigger_path(@project, trigger), method: :get, title: "Edit", class: "btn btn-default btn-sm" do
+      = link_to edit_project_trigger_path(@project, trigger), method: :get, title: "Edit", class: "btn btn-secondary btn-sm" do
         %i.fa.fa-pencil
     - if can?(current_user, :manage_trigger, trigger)
-      = link_to project_trigger_path(@project, trigger), data: { confirm: revoke_trigger_confirmation }, method: :delete, title: "Revoke", class: "btn btn-default btn-warning btn-sm btn-trigger-revoke" do
+      = link_to project_trigger_path(@project, trigger), data: { confirm: revoke_trigger_confirmation }, method: :delete, title: "Revoke", class: "btn btn-secondary btn-warning btn-sm btn-trigger-revoke" do
         %i.fa.fa-trash
diff --git a/app/views/projects/wikis/edit.html.haml b/app/views/projects/wikis/edit.html.haml
index 9d3d4072027..1ee820d96e0 100644
--- a/app/views/projects/wikis/edit.html.haml
+++ b/app/views/projects/wikis/edit.html.haml
@@ -4,7 +4,7 @@
 = wiki_page_errors(@error)
 
 .wiki-page-header.has-sidebar-toggle
-  %button.btn.btn-default.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
+  %button.btn.btn-secondary.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
     = icon('angle-double-left')
 
   .nav-text
diff --git a/app/views/projects/wikis/git_access.html.haml b/app/views/projects/wikis/git_access.html.haml
index 10dbbc0e42c..20a6b6c2c24 100644
--- a/app/views/projects/wikis/git_access.html.haml
+++ b/app/views/projects/wikis/git_access.html.haml
@@ -2,7 +2,7 @@
 - page_title s_("WikiClone|Git Access"), _("Wiki")
 
 .wiki-page-header.has-sidebar-toggle
-  %button.btn.btn-default.visible-xs.visible-sm.pull-right.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
+  %button.btn.btn-secondary.visible-xs.visible-sm.pull-right.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
     = icon('angle-double-left')
 
   .git-access-header
diff --git a/app/views/projects/wikis/history.html.haml b/app/views/projects/wikis/history.html.haml
index 969a1677d9a..e6451724208 100644
--- a/app/views/projects/wikis/history.html.haml
+++ b/app/views/projects/wikis/history.html.haml
@@ -1,7 +1,7 @@
 - page_title _("History"), @page.title.capitalize, _("Wiki")
 
 .wiki-page-header.has-sidebar-toggle
-  %button.btn.btn-default.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
+  %button.btn.btn-secondary.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
     = icon('angle-double-left')
 
   .nav-text
diff --git a/app/views/projects/wikis/show.html.haml b/app/views/projects/wikis/show.html.haml
index b3b83cee81a..df193740a39 100644
--- a/app/views/projects/wikis/show.html.haml
+++ b/app/views/projects/wikis/show.html.haml
@@ -5,7 +5,7 @@
 - add_to_breadcrumbs _("Wiki"), get_project_wiki_path(@project)
 
 .wiki-page-header.has-sidebar-toggle
-  %button.btn.btn-default.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
+  %button.btn.btn-secondary.sidebar-toggle.js-sidebar-wiki-toggle{ role: "button", type: "button" }
     = icon('angle-double-left')
 
   .nav-text
diff --git a/app/views/shared/_clone_panel.html.haml b/app/views/shared/_clone_panel.html.haml
index 687cd4d1532..351bb49493a 100644
--- a/app/views/shared/_clone_panel.html.haml
+++ b/app/views/shared/_clone_panel.html.haml
@@ -19,4 +19,4 @@
 
   = text_field_tag :project_clone, default_url_to_repo(project), class: "js-select-on-focus form-control", readonly: true, aria: { label: 'Project clone URL' }
   .input-group-btn
-    = clipboard_button(target: '#project_clone', title: _("Copy URL to clipboard"), class: "btn-default btn-clipboard")
+    = clipboard_button(target: '#project_clone', title: _("Copy URL to clipboard"), class: "btn-secondary btn-clipboard")
diff --git a/app/views/shared/_delete_label_modal.html.haml b/app/views/shared/_delete_label_modal.html.haml
index 01effefc34d..3b0fc9a8c30 100644
--- a/app/views/shared/_delete_label_modal.html.haml
+++ b/app/views/shared/_delete_label_modal.html.haml
@@ -11,7 +11,7 @@
           %span will be permanently deleted from #{label.is_a?(ProjectLabel)? label.project.name : label.group.name}. This cannot be undone.
 
       .modal-footer
-        %a{ href: '#', data: { dismiss: 'modal' }, class: 'btn btn-default' } Cancel
+        %a{ href: '#', data: { dismiss: 'modal' }, class: 'btn btn-secondary' } Cancel
 
         = link_to 'Delete label',
           destroy_label_path(label),
diff --git a/app/views/shared/_label.html.haml b/app/views/shared/_label.html.haml
index 56403907844..05928e42a6a 100644
--- a/app/views/shared/_label.html.haml
+++ b/app/views/shared/_label.html.haml
@@ -9,7 +9,7 @@
   = render "shared/label_row", label: label
 
   .visible-xs.visible-sm-inline-block.dropdown
-    %button.btn.btn-default.label-options-toggle{ type: 'button', data: { toggle: "dropdown" } }
+    %button.btn.btn-secondary.label-options-toggle{ type: 'button', data: { toggle: "dropdown" } }
       Options
       = icon('caret-down')
     .dropdown-menu.dropdown-menu-align-right
@@ -71,7 +71,7 @@
     - if current_user
       .label-subscription.inline
         - if can_subscribe_to_label_in_different_levels?(label)
-          %button.js-unsubscribe-button.label-subscribe-button.btn.btn-default{ type: 'button', class: ('hidden' if status.unsubscribed?), data: { url: toggle_subscription_path } }
+          %button.js-unsubscribe-button.label-subscribe-button.btn.btn-secondary{ type: 'button', class: ('hidden' if status.unsubscribed?), data: { url: toggle_subscription_path } }
             %span Unsubscribe
             = icon('spinner spin', class: 'label-subscribe-button-loading')
 
@@ -86,7 +86,7 @@
                 %a.js-subscribe-button{ class: ('hidden' unless status.unsubscribed?), data: { url: toggle_subscription_group_label_path(label.group, label) } }
                   Group level
         - else
-          %button.js-subscribe-button.label-subscribe-button.btn.btn-default{ type: 'button', data: { status: status, url: toggle_subscription_path } }
+          %button.js-subscribe-button.label-subscribe-button.btn.btn-secondary{ type: 'button', data: { status: status, url: toggle_subscription_path } }
             %span= label_subscription_toggle_button_text(label, @project)
             = icon('spinner spin', class: 'label-subscribe-button-loading')
 
diff --git a/app/views/shared/boards/components/_board.html.haml b/app/views/shared/boards/components/_board.html.haml
index 149bf8da4b9..0c1b1e6ebf8 100644
--- a/app/views/shared/boards/components/_board.html.haml
+++ b/app/views/shared/boards/components/_board.html.haml
@@ -27,7 +27,7 @@
           %span.issue-count-badge-count.pull-left{ ":class" => '{ "has-btn": list.type !== "closed" && !disabled }' }
             {{ list.issuesSize }}
           - if can?(current_user, :admin_list, current_board_parent)
-            %button.issue-count-badge-add-button.btn.btn-sm.btn-default.has-tooltip.js-no-trigger-collapse{ type: "button",
+            %button.issue-count-badge-add-button.btn.btn-sm.btn-secondary.has-tooltip.js-no-trigger-collapse{ type: "button",
               "@click" => "showNewIssueForm",
               "v-if" => 'list.type !== "closed"',
               "aria-label" => "New issue",
diff --git a/app/views/shared/issuable/_bulk_update_sidebar.html.haml b/app/views/shared/issuable/_bulk_update_sidebar.html.haml
index 0d507cc7a6e..d1cf8849510 100644
--- a/app/views/shared/issuable/_bulk_update_sidebar.html.haml
+++ b/app/views/shared/issuable/_bulk_update_sidebar.html.haml
@@ -6,7 +6,7 @@
       .block.issuable-sidebar-header
         .filter-item.inline.update-issues-btn.pull-left
           = button_tag "Update all", class: "btn update-selected-issues btn-info", disabled: true
-        = button_tag "Cancel", class: "btn btn-default js-bulk-update-menu-hide pull-right"
+        = button_tag "Cancel", class: "btn btn-secondary js-bulk-update-menu-hide pull-right"
       .block
         .title
           Status
diff --git a/app/views/shared/issuable/_label_page_create.html.haml b/app/views/shared/issuable/_label_page_create.html.haml
index 91aa329eb93..0a8a4db5a16 100644
--- a/app/views/shared/issuable/_label_page_create.html.haml
+++ b/app/views/shared/issuable/_label_page_create.html.haml
@@ -14,5 +14,5 @@
     .clearfix
       %button.btn.btn-primary.pull-left.js-new-label-btn{ type: "button" }
         = _('Create')
-      %button.btn.btn-default.pull-right.js-cancel-label-btn{ type: "button" }
+      %button.btn.btn-secondary.pull-right.js-cancel-label-btn{ type: "button" }
         = _('Cancel')
diff --git a/app/views/shared/issuable/_sidebar.html.haml b/app/views/shared/issuable/_sidebar.html.haml
index 975b9cb4729..e1498be4c51 100644
--- a/app/views/shared/issuable/_sidebar.html.haml
+++ b/app/views/shared/issuable/_sidebar.html.haml
@@ -146,7 +146,7 @@
           .sidebar-collapsed-icon{ data: { toggle: 'tooltip', placement: 'left', container: 'body' }, title: _('Move issue') }
             = custom_icon('icon_arrow_right')
           .dropdown.sidebar-move-issue-dropdown.hide-collapsed
-            %button.btn.btn-default.btn-block.js-sidebar-dropdown-toggle.js-move-issue{ type: 'button',
+            %button.btn.btn-secondary.btn-block.js-sidebar-dropdown-toggle.js-move-issue{ type: 'button',
               data: { toggle: 'dropdown' } }
               = _('Move issue')
             .dropdown-menu.dropdown-menu-selectable
diff --git a/app/views/shared/issuable/_sidebar_todo.html.haml b/app/views/shared/issuable/_sidebar_todo.html.haml
index b77e104c072..6732b064640 100644
--- a/app/views/shared/issuable/_sidebar_todo.html.haml
+++ b/app/views/shared/issuable/_sidebar_todo.html.haml
@@ -3,7 +3,7 @@
 - todo_content = is_collapsed ? icon('plus-square') : _('Add todo')
 
 %button.issuable-todo-btn.js-issuable-todo{ type: 'button',
-  class: (is_collapsed ? 'btn-blank sidebar-collapsed-icon dont-change-state has-tooltip' : 'btn btn-default issuable-header-btn pull-right'),
+  class: (is_collapsed ? 'btn-blank sidebar-collapsed-icon dont-change-state has-tooltip' : 'btn btn-secondary issuable-header-btn pull-right'),
   title: (todo.nil? ? _('Add todo') : _('Mark done')),
   'aria-label' => (todo.nil? ? _('Add todo') : _('Mark done')),
   data: issuable_todo_button_data(issuable, todo, is_collapsed) }
diff --git a/app/views/shared/members/_member.html.haml b/app/views/shared/members/_member.html.haml
index ba57d922c6d..8ecf1249f3a 100644
--- a/app/views/shared/members/_member.html.haml
+++ b/app/views/shared/members/_member.html.haml
@@ -53,7 +53,7 @@
         - if member.can_resend_invite?
           = link_to icon('paper-plane'), polymorphic_path([:resend_invite, member]),
                     method: :post,
-                    class: 'btn btn-default prepend-left-10 hidden-xs',
+                    class: 'btn btn-secondary prepend-left-10 hidden-xs',
                     title: 'Resend invite'
 
         - if user != current_user && member.can_update?
diff --git a/app/views/shared/milestones/_top.html.haml b/app/views/shared/milestones/_top.html.haml
index f302299eb24..d7c90c012aa 100644
--- a/app/views/shared/milestones/_top.html.haml
+++ b/app/views/shared/milestones/_top.html.haml
@@ -4,7 +4,7 @@
 - group = local_assigns[:group]
 
 .detail-page-header
-  %a.btn.btn-default.btn-grouped.pull-right.visible-xs-block.js-sidebar-toggle{ href: "#" }
+  %a.btn.btn-secondary.btn-grouped.pull-right.visible-xs-block.js-sidebar-toggle{ href: "#" }
     = icon('angle-double-left')
 
   .status-box{ class: "status-box-#{milestone.closed? ? 'closed' : 'open'}" }
diff --git a/app/views/shared/notes/_hints.html.haml b/app/views/shared/notes/_hints.html.haml
index bc1ac3d8ac2..cb3598db032 100644
--- a/app/views/shared/notes/_hints.html.haml
+++ b/app/views/shared/notes/_hints.html.haml
@@ -32,4 +32,4 @@
       = icon('file-image-o', class: 'toolbar-button-icon')
       Attach a file
 
-    %button.btn.btn-default.btn-xs.hide.button-cancel-uploading-files{ type: 'button' } Cancel
+    %button.btn.btn-secondary.btn-xs.hide.button-cancel-uploading-files{ type: 'button' } Cancel
diff --git a/app/views/shared/notifications/_button.html.haml b/app/views/shared/notifications/_button.html.haml
index e99d8d0973f..c5dd09f5826 100644
--- a/app/views/shared/notifications/_button.html.haml
+++ b/app/views/shared/notifications/_button.html.haml
@@ -6,14 +6,14 @@
       .js-notification-toggle-btns
         %div{ class: ("btn-group" if notification_setting.custom?) }
           - if notification_setting.custom?
-            %button.dropdown-new.btn.btn-default.has-tooltip.notifications-btn#notifications-button{ type: "button", title: "Notification setting", "aria-label" => "Notification setting: #{notification_title(notification_setting.level)}", data: { container: "body", toggle: "modal", target: "#" + notifications_menu_identifier("modal", notification_setting) } }
+            %button.dropdown-new.btn.btn-secondary.has-tooltip.notifications-btn#notifications-button{ type: "button", title: "Notification setting", "aria-label" => "Notification setting: #{notification_title(notification_setting.level)}", data: { container: "body", toggle: "modal", target: "#" + notifications_menu_identifier("modal", notification_setting) } }
               = icon("bell", class: "js-notification-loading")
               = notification_title(notification_setting.level)
             %button.btn.dropdown-toggle{ data: { toggle: "dropdown", target: notifications_menu_identifier("dropdown", notification_setting) } }
               = icon('caret-down')
               .sr-only Toggle dropdown
           - else
-            %button.dropdown-new.btn.btn-default.has-tooltip.notifications-btn#notifications-button{ type: "button", title: "Notification setting", "aria-label" => "Notification setting: #{notification_title(notification_setting.level)}", data: { container: "body", toggle: "dropdown", target: notifications_menu_identifier("dropdown", notification_setting) } }
+            %button.dropdown-new.btn.btn-secondary.has-tooltip.notifications-btn#notifications-button{ type: "button", title: "Notification setting", "aria-label" => "Notification setting: #{notification_title(notification_setting.level)}", data: { container: "body", toggle: "dropdown", target: notifications_menu_identifier("dropdown", notification_setting) } }
               = icon("bell", class: "js-notification-loading")
               = notification_title(notification_setting.level)
               = icon("caret-down")
diff --git a/app/views/snippets/_actions.html.haml b/app/views/snippets/_actions.html.haml
index a7f118d3f7d..f7f258a410b 100644
--- a/app/views/snippets/_actions.html.haml
+++ b/app/views/snippets/_actions.html.haml
@@ -12,7 +12,7 @@
   - if @snippet.submittable_as_spam_by?(current_user)
     = link_to 'Submit as spam', mark_as_spam_snippet_path(@snippet), method: :post, class: 'btn btn-grouped btn-spam', title: 'Submit as spam'
 .visible-xs-block.dropdown
-  %button.btn.btn-default.btn-block.append-bottom-0.prepend-top-5{ data: { toggle: "dropdown" } }
+  %button.btn.btn-secondary.btn-block.append-bottom-0.prepend-top-5{ data: { toggle: "dropdown" } }
     Options
     = icon('caret-down')
   .dropdown-menu.dropdown-menu-full-width