--- layout: docs title: Customization options group: getting-started --- Customize Bootstrap 4 with our built-in custom variables file and easily toggle global CSS preferences with new `$enable-*` Sass variables. Override a variable's value and recompile with the included Gruntfile as needed. ## Customizing variables Bootstrap 4 ships with a `_custom.scss` file for easy variable overrides. Copy and paste relevant lines from `_variables.scss` into the custom file and recompile your Sass to change our default values. **Be sure to remove the `!default` flag from override values.** For example, to change out the `background-color` and `color` for the ``, you'd do the following: {% highlight scss %} // Bootstrap overrides // // Copy variables from `_variables.scss` to this file to override default values // without modifying source files. $body-bg: $gray-dark; $body-color: $gray-light; {% endhighlight %} Do the same for any variable you need to override, including the global options listed below. ## Global options You can find and customize these variables for key global options in our `_variables.scss` file. | Variable | Values | Description | | --------------------------- | ---------------------------------- | -------------------------------------------------------------------------------------- | | `$spacer` | `1rem` (default), or any value > 0 | Specifies the default spacer value for our spacer utilities. | | `$enable-flex` | `true` or `false` (default) | Swaps `float` and `display: table` styles for `display: flex`. | | `$enable-rounded` | `true` (default) or `false` | Enables predefined `border-radius` styles on various components. | | `$enable-shadows` | `true` or `false` (default) | Enables predefined `box-shadow` styles on various components. | | `$enable-gradients` | `true` or `false` (default) | Enables predefined gradients via `background-image` styles on various components. | | `$enable-transitions` | `true` (default) or `false` | Enables predefined `transition`s on various components. | | `$enable-hover-media-query` | `true` or `false` (default) | ... | | `$enable-grid-classes` | `true` (default) or `false` | Enables the generation of CSS classes for the grid system (e.g. `.col-md-1` etc.). |