Browsers and devices

Supported browsers

CoreUI for Bootstrap supports the latest, stable releases of all major browsers and platforms.

Alternative browsers which use the latest version of WebKit, Blink, or Gecko, whether directly or via the platform’s web view API, are not explicitly supported. However, CoreUI for Bootstrap should (in most cases) display and function correctly in these browsers as well. More specific support information is provided below.

The floor is set by the platform features v6 depends on, with no fallbacks shipped: Chrome 123, Edge 123, Firefox 130, Safari 18 and iOS 18. Together with the evergreen lines below, this covers about 88% of global usage as measured with npx browserslist --coverage.

Why these versions?

Each floor is set by the newest feature v6 already requires, because the floor has to hold for the whole 6.x line:

A browser below the floor does not merely lose polish. An unsupported :has() invalidates the whole rule it appears in, unresolved light-dark() leaves colors unset, and a Safari 17 renders the palette with rotated hues — nothing fails, the colours are just not the ones you set. Where details.name reads back undefined, an exclusive accordion stops closing its siblings and every panel can stand open at once. @property is the quietest of them and the one worth knowing about: without it the registrations are ignored, custom properties inherit again, and a colour or opacity utility on a container tints everything nested inside it.

Versions come from MDN’s browser compatibility data. Note that caniuse does not track @property, @starting-style or transition-behavior at all, so browserslist "supports …" cannot answer for them.

You can find our supported range of browsers and their versions in our .browserslistrc file:

last 2 major versions
not dead
unreleased versions

Chrome >= 123
Edge >= 123
Firefox >= 130
iOS >= 18
Safari >= 18

not and_uc > 0
not and_qq > 0
not kaios > 0
not op_mini all

We use Autoprefixer to handle intended browser support via CSS prefixes, which uses Browserslist to manage these browser versions. Consult their documentation for how to integrate these tools into your projects.

How to read the query list

Two lines of that file do more than they look like they do:

• last 2 major versions carries the mobile coverage. caniuse tracks Chrome for Android as a single unversioned entry rather than one entry per release, so this line, not the >= floors, is what picks it up.
• unreleased versions is worth several points of coverage and costs nothing. caniuse gives the newest Safari a null release date while that version already holds most of Safari’s usage share, and both range queries and last N versions skip unreleased versions. The line cannot pull in anything old, because an unreleased version is newer than every floor.

The not … exclusions drop proxy and niche browsers that cannot run the floor features anyway; keeping them in the query would only grow the compiled CSS with legacy vendor prefixes.

To measure coverage yourself, run npx browserslist --coverage in a clone of the repository.

Modern platform features

The floor table above names what sets each floor; this is the fuller inventory of platform features v6 leans on:

Also safe to use

The floors clear more of the platform than the library currently uses. Everything below needs no fallback, no vendor prefix, and no polyfill anywhere in the supported range, so reach for it freely when you build on top of CoreUI:

• Native CSS nesting (Chrome 120, Firefox 117, Safari 17.2)
• text-wrap: balance (Chrome 114, Firefox 121, Safari 17.5)
• :focus-visible for keyboard-only focus styling
• Container query units and subgrid
• Dynamic viewport units (dvh, dvw) — the library itself sizes scrollable menus with dvh
• The popover attribute (Chrome 114, Firefox 125, Safari 17)

Versions come from MDN’s browser compatibility data, same as the floor table.

Not available yet

These sit above at least one of our floors, so v6 cannot rely on them without a fallback — and neither should you if you target the same range. With Safari at 18, Firefox is now the blocker most of the time:

One of these the library already touches, carefully: interpolate-size sits behind @supports, so accordions and collapses animate to their intrinsic height where it exists and jump without it, and the opt-in .transition-size class does nothing at all without it. Unprefixed backdrop-filter, content-visibility and relative color syntax with number channel values landed in Safari 18 and are inside the floor now. Anchor positioning is the one most worth waiting for — it would let Menu, Tooltip, Popover and Combobox drop their Floating UI dependency. Re-check these before you assume one has landed.

JavaScript

Every browser meeting the CSS floor above fully supports ES modules and the DOM APIs our plugins use — no transpilation or polyfills are required or provided. Both builds work across the whole range: the UMD bundles (coreui.js, exposing the coreui global) and the ES modules (coreui.esm.js). See JavaScript for loading patterns.

Mobile devices

Generally speaking, CoreUI for Bootstrap supports the latest versions of each major platform’s default browsers. Proxy browsers (such as Opera Mini, Opera Mobile’s Turbo mode, UC Browser Mini, Amazon Silk) are not supported.

For Firefox, in addition to the latest normal stable release, we also support the latest Extended Support Release (ESR) version of Firefox.

As always, make sure you include the responsive viewport meta tag in your <head> for proper rendering on mobile devices:

<meta name="viewport" content="width=device-width, initial-scale=1">

Internet Explorer

Internet Explorer is not supported. If you require Internet Explorer support, please use CoreUI v3. If you need the previous browser floors (Chrome 60+, Safari 12+), stay on CoreUI v5.