biome

Biome Skill

Configure and use Biome for fast JavaScript/TypeScript linting and formatting.

When to Use

• Setting up Biome in a project
• Migrating from ESLint/Prettier to Biome
• Configuring lint rules
• Formatting code with Biome

Critical Rules

Adopt Existing Conventions

If biome.json or biome.jsonc exists in the project:

• Read and adopt the existing configuration
• Do not modify existing rules without explicit request
• Follow the established formatting style (indent, line width, etc.)
• Respect any disabled rules or custom overrides
• Use the project's Biome version specified in package.json

Configuration

• Use biome.json or biome.jsonc for configuration
• Extend recommended rules as base
• Configure formatter and linter together
• Set up import organization

Performance

• Biome is 10-100x faster than ESLint/Prettier
• Use for CI/CD pipelines
• Format on save in editor
• Run checks in pre-commit hooks

Migration

• Start with biome migrate from ESLint/Prettier configs
• Disable conflicting rules gradually
• Maintain parity during transition
• Remove old configs after migration complete

Best Practices

• Enable all recommended rules by default
• Use biome check for lint + format in CI
• Configure import sorting
• Set up editor integration

Examples

biome.json

{
  "$schema": "https://biomejs.dev/schemas/1.5.3/schema.json",
  "organizeImports": {
    "enabled": true
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "correctness": {
        "noUnusedVariables": "error"
      }
    }
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 80
  }
}

Commands

# Check lint and format
biome check .

# Check with auto-fix
biome check --apply .

# Format only
biome format --write .

# Lint only
biome lint --apply .

Related

• /typescript - TypeScript best practices
• /react - React patterns that Biome enforces