slim-select

The native HTML select box has not meaningfully changed since the 1990s, and every design system eventually has to replace it. Slim Select is that replacement: single and multi-select, search with highlighting, option groups with select-all, remote data loading, and a modal mode that becomes a centered panel with a backdrop on mobile. MIT licensed, free, and maintained since 2017.

The pitch is that it stays out of your way. Zero dependencies, roughly 16KB of JavaScript gzipped plus 2KB of CSS, TypeScript types included, and theming through CSS custom properties instead of fighting class specificity. It ships WCAG 2.1 Level AA accessibility with real keyboard and screen reader support, which is the part most homegrown dropdowns get wrong. Official Vue 3 and React wrappers exist, or drop it into vanilla JS in two lines.

There is no paid tier and nothing gated. Solo devs, small teams, large teams get the same library. If you want alternatives in the same weight class, Choices.js and Tom Select cover similar ground, and react-select has a deeper ecosystem if you have already committed to React.

The catch is that a form component this central is one you live with for years, and this is a small-maintainer project. Check the issue tracker cadence before you commit, and vendor the source if that risk matters to you. The accessibility work is also only as good as your implementation: drop it into a form with no labels and no amount of ARIA in the library saves you.