Bootstrap 6 alpha moves customization toward CSS variables and native elements

Bootstrap 6’s first alpha replaces its older Sass import approach with modules and moves visual customization into CSS-variable token maps. JavaScript plugins become ESM-only, while native dialog and disclosure elements take over some component behavior. These changes also raise the minimum browser versions and alter responsive class naming. Existing Bootstrap users should treat it as a migration preview, not a routine dependency update.

Bootstrap · Oct 8, 2026

Why it matters

Framework upgrades can change browser coverage, build configuration and markup conventions together.

More context

Alpha 1 is published on npm and jsDelivr. The announcement lists Chrome and Edge 130, Firefox 132 and Safari 18 as its browser floor. Try a separate branch using the migration guide; CommonJS consumers need ESM imports, and custom Sass must move to the module system.

Keep in mind

The release is explicitly alpha and can change before beta. Bootstrap 5 remains supported for projects that cannot adopt the newer browser requirements.

Original read