Biome

Biome replaces ESLint and Prettier with a single tool, ending the config fights and the slow lint runs. It formats and lints JavaScript, TypeScript, JSX, JSON, CSS, and GraphQL in one pass, with HTML behind an opt-in. Written in Rust, so the speed is the point: the project's own benchmarks put it around 25 to 35 times faster than Prettier and about 15 times faster than ESLint without plugins.

Everything is free, dual licensed under MIT or Apache 2.0. There is nothing to host. Install it, keep one config file, run it. The enterprise page is contributors offering paid support, not a gated edition. Version 2 added type-aware lint rules that do not need the TypeScript compiler, and the rule count has passed 500, including React hooks rules, an accessibility group, and import sorting with custom groups.

Solo: switch unless your ESLint setup is heavily customized. Small teams: one config replaces two, with less bikeshedding. Medium and large: the CI time saved adds up, so test it on one project first. oxc-project/oxc is the other Rust contender worth a look for linting alone.

The catch is at the edges. Vue, Svelte, and Astro support is experimental, and SCSS, YAML, and Markdown are still in progress. Plugins are written in GritQL, so custom ESLint plugins do not carry over. And the type-aware floating promise rule catches about 75% of what typescript-eslint does, by Biome's own count.