Bootstrap is built to work best with the latest techniques. As such, older desktop and mobile browsers may display differently, but should remain fully functional.
Bootstrap supports the **latest, stable releases** of all major browsers and platforms. On Windows, **we support Internet Explorer 9-11**. More specific support information is provided below.
Unofficially, Bootstrap should look and behave well enough in Chromium and Chrome for Linux, Firefox for Linux, and Internet Explorer 8-, though they are not officially supported.
As of v4, Bootstrap no longer supports IE8. **If you require IE8 support, we recommend you use Bootstrap 3.** It's still supported by our team for bugfixes and documentation changes, but no new features will be added to it.
Alternatively, you can add the some third party JavaScript to backfill support for the browser. You'll need the following:
Bootstrap is not supported in the old Internet Explorer compatibility modes. To be sure you're using the latest rendering mode for IE, consider including the appropriate `<meta>` tag in your pages:
Confirm the document mode by opening the debugging tools: press <kbd>F12</kbd> and check the "Document Mode".
This tag is included in all of Bootstrap's documentation and examples to ensure the best rendering possible in each supported version of Internet Explorer.
See [this StackOverflow question](https://stackoverflow.com/questions/6771258/whats-the-difference-if-meta-http-equiv-x-ua-compatible-content-ie-edge) for more information.
Internet Explorer 10 in Windows Phone 8 versions older than [Update 3 (a.k.a. GDR3)](http://blogs.windows.com/windows_phone/b/wpdev/archive/2013/10/14/introducing-windows-phone-preview-for-developers.aspx) doesn't differentiate **device width** from **viewport width** in `@-ms-viewport` at-rules, and thus doesn't properly apply the media queries in Bootstrap's CSS. To address this, you'll need to **include the following JavaScript to work around the bug**.
Support for `overflow: hidden;` on the `<body>` element is quite limited in iOS and Android. To that end, when you scroll past the top or bottom of a modal in either of those devices' browsers, the `<body>` content will begin to scroll.
Also, note that if you're using a fixed navbar or using inputs within a modal, iOS has a rendering bug that doesn't update the position of fixed elements when the virtual keyboard is triggered. A few workarounds for this include transforming your elements to `position: absolute;` or invoking a timer on focus to try to correct the positioning manually. This is not handled by Bootstrap, so it is up to you to decide which solution is best for your application.
The `.dropdown-backdrop` element isn't used on iOS in the nav because of the complexity of z-indexing. Thus, to close dropdowns in navbars, you must directly click the dropdown element (or [any other element which will fire a click event in iOS](https://developer.mozilla.org/en-US/docs/Web/Events/click#Safari_Mobile)).
Page zooming inevitably presents rendering artifacts in some components, both in Bootstrap and the rest of the web. Depending on the issue, we may be able to fix it (search first and then open an issue if need be). However, we tend to ignore these as they often have no direct solution other than hacky workarounds.
Even though real hovering isn't possible on most touchscreens, most mobile browsers emulate hovering support and make `:hover` "sticky". In other words, `:hover` styles start applying after tapping an element and only stop applying after the user taps some other element. On mobile-first sites, this behavior is normally undesirable.
Bootstrap includes a workaround for this, although it is disabled by default. By setting `$use-hover-media-query` to `true` when compiling from Sass, Bootstrap will use [mq4-hover-shim](https://github.com/twbs/mq4-hover-shim) to disable `:hover` styles in browsers that emulate hovering, thus preventing sticky `:hover` styles. There are some caveats to this workaround; see the shim's documentation for details.
In particular, as of Chrome v32 and regardless of margin settings, Chrome uses a viewport width significantly narrower than the physical paper size when resolving media queries while printing a webpage. This can result in Bootstrap's extra-small grid being unexpectedly activated when printing. [See #12078 for some details.](https://github.com/twbs/bootstrap/issues/12078) Suggested workarounds:
Also, as of Safari v8.0, fixed-width <code>.container</code>s can cause Safari to use an unusually small font size when printing. See <ahref="https://github.com/twbs/bootstrap/issues/14868">#14868</a> for more details. One potential workaround for this is adding the following CSS:</p>
Out of the box, Android 4.1 (and even some newer releases apparently) ship with the Browser app as the default web browser of choice (as opposed to Chrome). Unfortunately, the Browser app has lots of bugs and inconsistencies with CSS in general.
On `<select>` elements, the Android stock browser will not display the side controls if there is a `border-radius` and/or `border` applied. (See [this StackOverflow question](https://stackoverflow.com/questions/14744437/html-select-box-not-showing-drop-down-arrow-on-android-version-4-0-when-set-with) for details.) Use the snippet of code below to remove the offending CSS and render the `<select>` as an unstyled element on the Android stock browser. The user agent sniffing avoids interference with Chrome, Safari, and Mozilla browsers.
In order to provide the best possible experience to old and buggy browsers, Bootstrap uses [CSS browser hacks](http://browserhacks.com) in several places to target special CSS to certain browser versions in order to work around bugs in the browsers themselves. These hacks understandably cause CSS validators to complain that they are invalid. In a couple places, we also use bleeding-edge CSS features that aren't yet fully standardized, but these are used purely for progressive enhancement.
These validation warnings don't matter in practice since the non-hacky portion of our CSS does fully validate and the hacky portions don't interfere with the proper functioning of the non-hacky portion, hence why we deliberately ignore these particular warnings.
Our HTML docs likewise have some trivial and inconsequential HTML validation warnings due to our inclusion of a workaround for [a certain Firefox bug](https://bugzilla.mozilla.org/show_bug.cgi?id=654072).
