Biome vs ESLint: Should You Switch? 0.41s vs 18.7s

On react-hook-form (317 files), Biome 2.5.15 check took a median 0.41 s. The same tree under ESLint 9.39.4 plus Prettier 3.8.4 took 18.7 s wall clock when I ran them back to back (ESLint alone 13.6 s, Prettier --check 5.2 s).

Short answer: switch if you want one tool for lint plus format and your rules are mostly what Biome already covers. Keep ESLint, or run both, if you lean on Playwright rules, type-only unused checks, or a deliberately relaxed any policy. No affiliate links in this post.

What I tested

• Machine: 8 vCPU Intel Xeon / 15 GB RAM Linux cloud box, Node 20.19.2, tested 5 Oct 2026 (about 22:35 to 22:45 IST). The box is shared, so I interleaved the tools each round.
• Repo: react-hook-form at commit 91856c2 (4 Oct 2026), installed from its own lockfile. Flat ESLint config: typescript-eslint 8.61.1 recommended, eslint-plugin-react, react-hooks, simple-import-sort, eslint-plugin-prettier, eslint-plugin-playwright. no-explicit-any is off in that config.
• Biome: 2.5.15 with a biome.json that enables recommended rules plus hooks and noConsole, and turns a11y recommended off so the run stays closer to the repo's ESLint set. Formatter set to 2-space, single quotes, trailing commas.
• Timing: three interleaved runs each; median wall-clock for the whole command. Also one sequential ESLint-then-Prettier pass for the stack total.
• Migration probe: biome migrate eslint on the repo config (no --write kept for the timed runs).
• One surprise: Biome's recommended set raised 287 noExplicitAny hits. The repo's ESLint config turns that rule off, so a naive "recommended Biome" swap is not a drop-in severity match.
• Not tested: Biome type-aware lint, editor extensions, autofix output diffs, Vue/Svelte, Windows/macOS.

Is Biome faster than ESLint plus Prettier?

Setup	Median	Runs
ESLint 9.39.4, repo config, single thread	13.58 s	13.47 / 15.11 / 13.58
ESLint, --concurrency auto	8.68 s	8.68 / 10.30 / 8.10
Prettier 3.8.4 --check (src, e2e, scripts, root configs)	5.22 s	5.39 / 5.22 / 5.12
ESLint then Prettier, sequential wall	18.74 s	one pass
Biome check (lint + format + assist)	0.41 s	0.41 / 0.40 / 0.42
Biome lint only	0.34 s	0.34 / 0.33 / 0.36
Biome format only	0.22 s	0.22 / 0.24 / 0.22

Biome checked 317 files. On this box, check was about 33x faster than single-thread ESLint and about 46x faster than the ESLint+Prettier stack. ESLint's own --concurrency auto cut lint to 8.7 s; it still did not close the gap. Formatting alone: Prettier --check 5.2 s vs Biome format 0.22 s (~24x).

For CI cold runs, the stack number is the one that matters. Local re-runs with ESLint --cache would look kinder; I did not re-measure cache here because the oxlint comparison on the same repo already covered that path.

Does Biome catch the same problems?

No. Counts on the same tree:

Tool	Files	Errors	Warnings	Notes
ESLint (repo config)	301 lintable	0	562	Mostly @typescript-eslint/no-unused-vars, including "only used as a type"
Biome check (recommended-ish)	317	200	427	Plus 118 infos; 9 of the errors were format mismatches

Top Biome categories were not a mirror of ESLint: 287 noExplicitAny, 64 organize-imports assists, 62 useOptionalChain, 47 useless lone blocks, 36 useHookAtTopLevel, and only 30 noUnusedVariables (plus 16 noUnusedImports). ESLint's 562 warnings were dominated by unused-vars in type-test files. Different rule defaults, different findings.

Format: Prettier reported every checked file clean. Biome format flagged 9 files, mostly line-break choices inside long TypeScript generics. That is a real migration cost even when lint is the reason you switched.

biome migrate eslint reported 476 ESLint rules in the expanded config: 54 migrate directly (plus 11 inspired, 16 nursery), about 50% (241) fully covered by Biome, and a long unsupported list that includes Playwright rules, prettier/prettier, and simple-import-sort/*. Keep those as a thin ESLint pass if you still need them. The Biome 2.5.15 release notes post covers what that version added for type inference and nursery rules.

How do I switch without losing checks?

1. Run biome migrate eslint (add --include-inspired if you want the extra matches) and read the unsupported list before you delete anything.
2. Diff severity. If your ESLint config turns no-explicit-any off, turn Biome's suspicious/noExplicitAny off too, or CI will fail on noise this repo never linted.
3. Move formatting deliberately. Compare biome format --write on a branch to Prettier; expect a handful of wrapping diffs even when --check was clean under Prettier. The oxfmt vs Prettier Markdown test is a related formatter decision if Markdown is in scope.
4. Keep ESLint for Playwright and any plugin Biome lists as unknown. Run Biome first in CI, then the thin ESLint set.
5. If you only want lint speed and already like Prettier, the oxlint vs ESLint switch post is the closer comparison; Biome's pitch is the combined lint+format binary.

Should you switch from ESLint and Prettier to Biome?

Situation	My pick
New or small TS/React app, standard rules, slow CI lint+format	Biome check as the default
Heavy Playwright / custom plugin / import-sort rules	Biome for the covered set, thin ESLint for the rest
Policy depends on allowing any or type-only unused vars	Tune Biome rules first; do not paste recommended blind
You already switched lint to oxlint and only need a faster formatter	Stay on oxlint + Prettier or oxfmt; Biome is optional
Vue / Svelte / custom parsers	Keep ESLint for those files for now

Bottom line: on this repo Biome turned an 18.7 s lint+format stack into a 0.41 s check, but it did not reproduce ESLint's warning set and it disagreed with Prettier on 9 files. Who should not switch yet: teams whose lint signal is mostly type-aware unused checks or Playwright plugins. Everyone else can take the speed if they migrate rules on purpose.

How this was made: I ran every command above on the ShopperCove test box and kept the raw JSON and timing logs; the write-up was drafted with AI help and checked against that output.

Sources

• https://github.com/react-hook-form/react-hook-form
• https://biomejs.dev/blog/biome-v2-5/
• https://biomejs.dev/guides/migrate-eslint-prettier/
• https://biomejs.dev/reference/cli/
• https://eslint.org/docs/latest/use/command-line-interface
• https://prettier.io/docs/cli
• https://www.npmjs.com/package/@biomejs/biome

Related

• https://www.shoppercove.com/blog/biome-2-5-15-type-inference-nursery-rules-october-2026
• https://www.shoppercove.com/blog/oxlint-vs-eslint
• https://www.shoppercove.com/blog/oxfmt-0-72-native-markdown-formatter-prettier-parity-october-2026
• https://www.shoppercove.com/blog/eslint-10-12-release-october-2026
• https://www.shoppercove.com/blog/typescript-eslint-8-71-no-unsafe-enum-assignment-october-2026
• https://www.shoppercove.com/blog/oxlint-1-87-react-suggestions-a11y-fixes-october-2026
• https://www.shoppercove.com/blog/vite-plus-1-0-unified-toolchain-october-2026
• https://www.shoppercove.com/blog/pnpm-vs-npm-vs-bun