Biome Lint and format JS/TS

Version 2.5 · source

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Dark · A3 297 × 420 mm · PDF

Ink saver · A3 297 × 420 mm · PDF

Light · A3 landscape 420 × 297 mm · PDF

Dark · A3 landscape 420 × 297 mm · PDF

Ink saver · A3 landscape 420 × 297 mm · PDF

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Start here

biome init

Create biome.json

biome check .

Format, lint, organise imports

biome check --write .

Apply safe fixes

biome format --write <path>

Format only

biome lint <path>

Lint only

biome ci .

Read-only check for CI

biome check --staged

Only staged files

biome explain <rule>

What a rule means

Concepts

biome check one pass, all three

Formatter layout

Linter rules, safe and unsafe fixes

Assist organise imports

Setup

npm i -D -E @biomejs/biome

Install pinned in a project

-E pins the exact version so formatting stays stable.

biome init

Create biome.json

biome init --jsonc

Create biome.jsonc instead

biome version

Print the CLI version

biome migrate --write

Update config after an upgrade

Run without --write first to preview the changes.

biome migrate prettier --write

Import Prettier settings

biome migrate eslint --write

Import ESLint settings

Add --include-inspired to also carry over rules Biome only approximates.

biome upgrade

Upgrade a standalone binary

Not for npm installs; bump the package instead.

Check

biome check <path>

Format, lint and assist, report only

biome check --write <path>

Apply formatting and safe fixes

--fix is an alias.

biome check --write --unsafe <path>

Also apply unsafe fixes

Review the diff; unsafe fixes can change behaviour.

biome check --staged

Only staged files

biome check --changed

Files changed versus the default branch

Needs vcs.defaultBranch set, or use --since.

biome check --changed --since=<ref>

Changed since a given ref

biome check --linter-enabled=false

Skip the linter for this run

biome check --formatter-enabled=false

Skip the formatter for this run

biome check --stdin-file-path=<file>

Process stdin to stdout

biome check --watch

Re-run when files change

Format

biome format <path>

Show formatting differences

biome format --write <path>

Format files in place

biome format --staged --write

Format staged files

biome format --indent-style=space

Use spaces instead of tabs

Biome defaults to tabs, unlike Prettier.

biome format --line-width=<n>

Set the line width

biome format --stdin-file-path=<file>

Format code piped on stdin

Lint

biome lint <path>

Lint only

biome lint --write <path>

Apply safe lint fixes

biome lint --write --unsafe <path>

Apply unsafe lint fixes too

biome lint --only=<rule>

Run a single rule or group

For example --only=suspicious or --only=correctness/noUnusedVariables.

biome lint --skip=<rule>

Turn a rule or group off for this run

biome lint --suppress --reason="<why>"

Add suppression comments to violations

Handy for adopting a rule on a big codebase gradually.

biome explain <rule>

Show docs for a rule

biome search '<pattern>'

Find code with a GritQL pattern

Experimental; add -l css or -l json for other languages.

CI & output

biome ci .

Check without modifying files

Fails on format, lint and assist problems; has no --write.

biome ci --changed

Only files changed on this branch

biome ci --reporter=github

Annotate a GitHub run

--reporter=<name>

Pick the output format

Includes json, junit, sarif, gitlab, summary and concise.

--reporter-file=<path>

Write report to a file

--error-on-warnings

Fail the run on warnings

--diagnostic-level=error

Show only errors

--max-diagnostics=none

Show every diagnostic

The default cuts the output at 20.

--no-errors-on-unmatched

Do not fail when no file matches

--threads=<n>

Limit parallelism in CI

Configuration

biome.json basics

{  "vcs": { "enabled": true, "clientKind": "git",           "useIgnoreFile": true, "defaultBranch": "main" },  "files": { "includes": ["src/**"] },  "formatter": { "indentStyle": "space", "lineWidth": 100 },  "linter": { "rules": { "preset": "recommended" } }}

--config-path=<dir>

Use a config from another folder

biome rage

Print a troubleshooting report

Config sections

Key	Controls
`formatter`	indent, width, line ending
`linter`	rules and their severity
`javascript.formatter`	quotes, semicolons, commas
`assist`	import organising and other actions
`overrides`	per-glob settings

Editor & hooks

biome lsp-proxy

Run the language server over stdio

biome start

Start the background daemon

biome stop

Stop the background daemon

biome clean

Remove daemon log files

Recipes

Adopt in an existing project

npm i -D -E @biomejs/biomenpx biome initnpx biome migrate prettier --writenpx biome migrate eslint --writenpx biome check --write .

Pre-commit on staged files

# .git/hooks/pre-commitnpx biome check --staged --write --no-errors-on-unmatchedgit update-index --again

CI job

npx biome ci --reporter=github# or only this branchnpx biome ci --changed --since=origin/main

package.json scripts

"lint": "biome lint .","format": "biome format --write .","check": "biome check --write ."