Guidance on how to upgrade from Bootstrap v3.x to v4.x with emphasis on major changes, what's new, and what's been removed.
Bootstrap 4 is a major rewrite of almost the entire project. The most notable changes are summarized immediately below, followed by more specific class and behavioral changes to relevant components.
Heads up! This will be in flux as work on the v4 alphas progresses. Until then consider it incomplete, and we’d love pull requests to help keep it up to date.
Here are the big ticket items you’ll want to be aware of when moving from v3 to v4.
px to rem as our primary CSS unit, though pixels are still used for media queries and grid behavior as viewports are not affected by type size.14px to 16px.576px and below (our new xs tier).$enable-gradients: true).make-col-span into make-col for a singular mixin.sm grid tier below 768px for more granular control. We now have xs, sm, md, lg, and xl. This also means every tier has been bumped up one level (so .col-md-6 in v3 is now .col-lg-6 in v4).12 at their max width.$grid-breakpoints and $container-max-widths) instead of a handful of separate variables. These replace the @screen-* variables entirely and allow you to fully customize the grid tiers.@include media-breakpoint-up/down/only. Now, instead of writing @media (min-width: @screen-sm-min) { ... }, you can write @include media-breakpoint-up(sm) { ... }.position: sticky polyfill instead. See the HTML5 Please entry for details and specific polyfill recommendations.
position styles, the polyfills might not support your use case. One option for such uses is the third-party ScrollPos-Styler library.This list highlights key changes by component between v3.x.x and v4.0.0.
New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with our own somewhat opinionated reset styles. Selectors appearing in this file only use elements—there are no classes here. This isolates our reset styles from our component styles for a more modular approach. Some of the most important resets this includes are the box-sizing: border-box change, moving from em to rem units on many elements, link styles, and many form element resets.
.text- utilities to the _utilities.scss file..page-header as, aside from the border, all its styles can be applied via utilities..dl-horizontal has been dropped. Instead, use .row on <dl> and use grid column classes (or mixins) on its <dt> and <dd> children.<blockquote> styling has moved to classes—.blockquote and the .blockquote-reverse modifier..list-inline now requires that its children list items have the new .list-inline-item class applied to them..img-responsive to .img-fluid..img-rounded to .rounded.img-circle to .rounded-circle> selector have been removed, meaning nested tables will now automatically inherit styles from their parents. This greatly simplifies our selectors and potential customizations..table-responsive right on the <table>..table-condensed to .table-sm for consistency..table-inverse option..thead-default and .thead-inverse..table--prefix. Hence .active, .success, .warning, .danger and .table-info to .table-active, .table-success, .table-warning, .table-danger and .table-info._reboot.scss file..control-label to .form-control-label..input-lg and .input-sm to .form-control-lg and .form-control-sm, respectively..form-group-* classes for simplicity’s sake. Use .form-control-* classes instead now..help-block and replaced it with .form-text for block-level help text. For inline help text and other flexible options, use utility classes like .text-muted..form-horizontal class requirement..form-group no longer applies styles from the .row via mixin, so .row is now required for horizontal grid layouts (e.g., <div class="form-group row">)..form-control-label class to vertically center labels with .form-controls..btn-default to .btn-secondary..btn-xs class entirely as .btn-sm is proportionally much smaller than v3’s.button.js jQuery plugin has been dropped. This includes the $().button(string) and $().button('reset') methods. We advise using a tiny bit of custom JavaScript instead, which will have the benefit of behaving exactly the way you want it to.
.btn-group-justified..btn-group-xs class entirely given removal of .btn-xs.<div>s or <ul>s now.<a> and <button> based dropdown items..divider to .dropdown-divider..dropdown-item.<span class="caret"></span>; this is now provided automatically via CSS’s ::after on .dropdown-toggle.576px grid breakpoint as sm, meaning there are now five total tiers (xs, sm, md, lg, and xl)..col-{breakpoint}-{modifier}-{size} to .{modifier}-{breakpoint}-{size} for simpler grid classes. For example, instead of .col-md-3.col-md-push-9 it’s .col-md-3.push-md-9.make-col and make-col-span into a single make-col mixin, thereby ensuring mixins and predefined classes utilize the same float/flex behaviors.a.list-group-item with an explicit class, .list-group-item-action, for styling link and button versions of list group items..list-group-flush class for use with cards.remote option (which could be used to automatically load and inject external content into a modal) and the corresponding loaded.bs.modal event were removed. We recommend instead using client-side templating or a data binding framework, or calling jQuery.load yourself.> selectors for simpler styling via un-nested classes..nav > li > a, we use separate classes for .navs, .nav-items, and .nav-links. This makes your HTML more flexible while bringing along increased extensibility.The navbar has been entirely rewritten in flexbox with improved support for alignment, responsiveness, and customization.
.navbar class via the required .navbar-expand-{breakpoint} where you choose where to collapse the navbar. Previously this was a Less variable modification and required recompiling..navbar-default is now .navbar-light, though .navbar-inverse remains the same. One of these is required on each navbar. However, these classes no longer set background-colors; instead they essentiatlly only affect color..bg-*) or set your own with the light/inverse classes above for mad customization..navbar-toggle is now .navbar-toggler and has different styles and inner markup (no more three <span>s)..navbar-form class entirely. It’s no longer necessary; instead, just use .form-inline and apply margin utilities as necessary.margin-bottom or border-radius by default. Use utilities as necessary..page-item, .page-link) are now required on the descendants of .paginations.pager component entirely as it was little more than customized outline buttons..breadcrumb-item, is now required on the descendants of .breadcrumbs.label to .badge to disambiguate from the <label> element..badge component as it was nearly identical to labels. Use the .badge-pill modifier together with the label component instead for that rounded look.Dropped entirely for the new card component.
.panel to .card, now built with flexbox..panel-default removed and no replacement..panel-group removed and no replacement. .card-group is not a replacement, it is different..panel-heading to .card-header.panel-title to .card-title. Depending on the desired look, you may also want to use heading elements or classes (e.g. <h3>, .h3) or bold elements or classes (e.g. <strong>, <b>, .font-weight-bold). Note that .card-title, while similarly named, produces a different look than .panel-title..panel-body to .card-block.panel-footer to .card-footer.panel-primary to .card-primary and .card-inverse (or use .bg-primary on .card-header).panel-success to .card-success and .card-inverse (or use .bg-success on .card-header).panel-info to .card-info and .card-inverse (or use .bg-info on .card-header).panel-warning to .card-warning and .card-inverse (or use .bg-warning on .card-header).panel-danger to .card-danger and .card-inverse (or use .bg-danger on .card-header)auto placement options.auto placement options..carousel-.
.next, .prev, .left, and .right are now .carousel-item-next, .carousel-item-prev, .carousel-item-left, and .carousel-item-right..item is also now .carousel-item..carousel-control.right and .carousel-control.left are now .carousel-control-right and .carousel-control-left, meaning they no longer require a specific base class..d-none and d-{sm,md,lg,xl}-none)..float-{sm,md,lg,xl}-{left,right,none} classes for responsive floats and removed .pull-left and .pull-right since they’re redundant to .float-left and .float-right..text-{sm,md,lg,xl}-{left,center,right}..center-block for the new .mx-auto class.Bootstrap 3’s vendor prefix mixins, which were deprecated in v3.2.0, have been removed in Bootstrap 4. Since we use Autoprefixer, they’re no longer necessary.
Removed the following mixins: animation, animation-delay, animation-direction, animation-duration, animation-fill-mode, animation-iteration-count, animation-name, animation-timing-function, backface-visibility, box-sizing, content-columns, hyphens, opacity, perspective, perspective-origin, rotate, rotateX, rotateY, scale, scaleX, scaleY, skew, transform-origin, transition-delay, transition-duration, transition-property, transition-timing-function, transition-transform, translate, translate3d, user-select
Our documentation received an upgrade across the board as well. Here’s the low down:
example.rb is a fork of the default highlight.rb plugin, allowing for easier example-code handling.callout.rb is a similar fork of that, but designed for our special docs callouts.All @screen- variables have been removed in v4.0.0. Use the media-breakpoint-up(), media-breakpoint-down(), or media-breakpoint-only() Sass mixins or the $grid-breakpoints Sass map instead.
Our responsive utility classes have largely been removed in favor of explicit display utilities.
.hidden and .show classes have been removed because they conflicted with jQuery’s $(...).hide() and $(...).show() methods. Instead, try toggling the [hidden] attribute or use inline styles like style="display: none;" and style="display: block;"..hidden- classes have been removed, save for the print utilities which have been renamed.
.hidden-xs .hidden-sm .hidden-md .hidden-lg .visible-xs-block .visible-xs-inline .visible-xs-inline-block .visible-sm-block .visible-sm-inline .visible-sm-inline-block .visible-md-block .visible-md-inline .visible-md-inline-block .visible-lg-block .visible-lg-inline .visible-lg-inline-block.hidden-xs-up .hidden-xs-down .hidden-sm-up .hidden-sm-down .hidden-md-up .hidden-md-down .hidden-lg-up .hidden-lg-down.hidden- or .visible-, but with .d-print-.
.visible-print-block, .visible-print-inline, .visible-print-inline-block, .hidden-print.d-print-block, .d-print-inline, .d-print-inline-block, .d-print-noneRather than using explicit .visible-* classes, you make an element visible by simply not hiding it at that screen size. You can combine one .d-*-none class with one .d-*-block class to show an element only on a given interval of screen sizes (e.g. .d-none.d-md-block.d-lg-none shows the element only on medium and large devices).
Note that the changes to the grid breakpoints in v4 means that you’ll need to go one breakpoint larger to achieve the same results. The new responsive utility classes don’t attempt to accommodate less common cases where an element’s visibility can’t be expressed as a single contiguous range of viewport sizes; you will instead need to use custom CSS in such cases.
min--moz-device-pixel-ratio typo hack for retina media queries[disabled] to :disabled as IE9+ supports :disabled. However fieldset[disabled] is still necessary because native disabled fieldsets are still buggy in IE11.TODO: audit list of stuff in v3 that was marked as deprecated