Bootstrap 5.3 Released: Dark Mode and Custom Color Modes

What happened

Bootstrap 5.3.0 was released on May 30, 2023, according to the official Bootstrap blog and GitHub release. Creator Mark Otto described it as a monumental effort to revamp the codebase for CSS variables and color modes, part of a continued evolution leading toward an eventual Bootstrap 6.

Dark mode

The headline feature was first-class dark mode support. Bootstrap's core was rewritten so that dark mode is opt-in via a data-bs-theme attribute on the root html element, or scoped to a parent element such as a dropdown. The mode is powered by a new color-mode() Sass mixin and a _variables-dark.scss stylesheet, with dark-mode colors all derived from the existing theme colors.

Custom color modes

Rather than adding only a dark mode, Bootstrap 5.3 built the foundations for a color-mode system that can support any number of themes. Developers can create a custom color mode, such as a blue theme, by defining their own data-bs-theme selector value and overriding Sass or CSS variables. A $color-mode-type Sass variable also lets modes be generated as data attributes or as prefers-color-scheme media queries.

Palette, links and utilities

The release revamped the color palette with new Sass and CSS variables and utilities, expanding foreground and background colors with secondary, tertiary and emphasis variants plus subtle background, subtle border and darker text colors. It added an icon-link helper, a focus-ring helper, new link-opacity and link-underline utilities, a link-body-emphasis helper, and a new nav-underline variant, while deprecating the text-muted utility in favour of text-body-secondary.

Why it mattered

Bootstrap 5.3 modernised one of the web's most widely used CSS frameworks for the color-mode era. Bringing first-class dark mode and a general color-mode system, all built on CSS variables, gave the framework's enormous user base a standards-aligned way to support theming without leaving Bootstrap.

Related on Skillo

See also: Bootstrap 5.2 and CSS variables.

Sources

• Bootstrap 5.3.0 (official Bootstrap blog)

Published date reflects the original event date (2023-05-30). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.