LLM Best Practices

ESLint vs Biome

3 min read

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Overview

Use Biome on new projects. It combines a linter and formatter into one fast tool, eliminates Prettier as a separate dependency, and requires no plugin config for standard JavaScript and TypeScript. Use ESLint when your project requires plugins without Biome equivalents: eslint-plugin-import, eslint-plugin-react-hooks, accessibility rules from eslint-plugin-jsx-a11y, or custom corporate rule sets. See swc-vs-babel for the adjacent build-tool decision.

When Biome wins

Biome is the right choice when the linting and formatting requirements are standard.

  • Speed: Biome is written in Rust and runs lint and format in a single pass. On a 1000-file TypeScript project it typically completes in under 500 ms; ESLint with Prettier on the same project takes 5 to 15 seconds.
  • Single tool: Biome replaces both ESLint and Prettier. One config file (biome.json), one dev dependency, one CI step.
  • Zero config for TypeScript: biome check . works out of the box on TypeScript, JSX, and JSON without plugins or parser overrides.
  • Consistent formatting: Biome’s formatter is intentionally Prettier-compatible for most cases, so a migration from Prettier produces minimal diffs.
  • No plugin hell: ESLint v8 to v9 flat config migration broke many plugins. Biome has no equivalent fragility.
// biome.json
{
  "linter": { "enabled": true, "rules": { "recommended": true } },
  "formatter": { "enabled": true, "indentStyle": "space", "indentWidth": 2 },
  "javascript": { "formatter": { "quoteStyle": "double" } }
}

When ESLint wins

ESLint is the right choice when plugin dependencies are real constraints.

  • eslint-plugin-react-hooks: enforces the Rules of Hooks. Biome’s React rule coverage is partial as of mid-2026; the hooks exhaustive-deps rule is not yet fully implemented.
  • eslint-plugin-import and eslint-plugin-boundaries: graph-based import ordering and boundary enforcement. No Biome equivalent yet.
  • eslint-plugin-jsx-a11y: accessibility linting for JSX. Critical for compliance-sensitive projects. Biome’s a11y rules cover some cases but not all.
  • Custom corporate rules: teams with internal eslint-plugin-company-* packages have no migration path to Biome.
  • Framework-specific rule sets: eslint-config-next, @angular-eslint, and Nx lint presets all target ESLint.

Running both Biome (for formatting) and ESLint (for rules) is a valid hybrid. Disable Biome’s linter and use it only for formatting, with ESLint handling rules.

Trade-offs at a glance

DimensionBiomeESLint (with Prettier)
SpeedVery fast (Rust, single pass)Slower; scales poorly past 500 files
SetupOne config file, zero plugins for basicsMultiple packages, possible parser conflicts
Formatting includedYesOnly via Prettier integration
TypeScript supportNativeVia @typescript-eslint/parser
Plugin ecosystemGrowing; 200+ rules built inMature; thousands of plugins
React Hooks rulesPartialFull via eslint-plugin-react-hooks
Accessibility rulesPartialFull via eslint-plugin-jsx-a11y
Custom rulesPlugins in developmentRich custom rule authoring
Config migration (v9)Not applicableFlat config migration required for v9+
Editor integrationVS Code extension, CLIAll editors; mature support

Migration cost

ESLint plus Prettier to Biome is typically low-effort for standard configurations.

  • npx @biomejs/biome migrate eslint --write reads eslint.config.* or .eslintrc.* and generates an initial biome.json. Handles common rule mappings automatically.
  • Run biome check --apply . to auto-fix formatting and auto-fixable lint issues. Review the diff.
  • Disable Prettier and ESLint in CI. Remove eslint, prettier, and related plugins from package.json.
  • Expect to lose some rules that have no Biome equivalent. Audit the ESLint rule list against the Biome rule reference before committing.
  • Effort: half a day for a 200-file project with a standard config; longer if custom plugins are in use.

Recommendation

  • New project with no special plugin requirements: Biome.
  • New React project: Biome for formatting; add ESLint with eslint-plugin-react-hooks for hooks enforcement until Biome’s coverage is complete.
  • Existing ESLint project, standard rules: migrate when you have CI time to spare. The speed win is real.
  • Existing ESLint project with custom plugins or strict a11y requirements: stay on ESLint.
  • Hybrid: valid. Use biome format only and ESLint for rules. Saves Prettier overhead without losing rule coverage.

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