Biome

Biome is a unified, high-performance toolchain written in Rust that provides sub-millisecond code formatting and linting for JavaScript, TypeScript, and JSON.

When to Use

• Ultra-Fast Rust-Powered Linter & Formatter: Formatting and linting JavaScript, TypeScript, JSX, and JSON 25x faster than Prettier/ESLint.
• Unified Toolchain Setup: Replacing separate ESLint, Prettier, and import-sorter configs with a single biome.json.
• Instant CI Verification: Checking formatting, imports, and syntax in sub-seconds in automated CI pipelines.
• Prettier & ESLint Migration: Automated zero-friction migration using biome migrate.

Quick Start

# Initialize Biome configuration in project
npx @biomejs/biome init

# Format and lint entire workspace in milliseconds
npx @biomejs/biome check --write ./src

Core Concepts

Declarative Configuration (biome.json)

Consolidating formatting, linting, and import sorting:

{
  "$schema": "https://biomejs.dev/schemas/1.9.0/schema.json",
  "vcs": {
    "enabled": true,
    "clientKind": "git",
    "useIgnoreFile": true
  },
  "formatter": {
    "enabled": true,
    "formatWithErrors": false,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 100
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "suspicious": {
        "noExplicitAny": "error"
      },
      "style": {
        "useConst": "error"
      }
    }
  },
  "organizeImports": {
    "enabled": true
  },
  "javascript": {
    "formatter": {
      "quoteStyle": "double",
      "semicolons": "always"
    }
  }
}

Biome CLI Execution in Workflows

Formatting, checking, and applying autofixes:

# Check formatting, lint rules, and import ordering
npx @biomejs/biome check .

# Automatically apply safe fixes and formatting across all files
npx @biomejs/biome check --write .

# Format only (drop-in Prettier replacement)
npx @biomejs/biome format --write ./src

# CI verification (fails with non-zero exit code if changes needed)
npx @biomejs/biome ci .

Migrating from Prettier & ESLint

Importing existing rules automatically:

# Migrate from Prettier configuration
npx @biomejs/biome migrate prettier --write

# Migrate from ESLint configuration
npx @biomejs/biome migrate eslint --write

Common Patterns

Complete biome.json Configuration with Recommended Rules

Problem: Slow CI linters (ESLint + Prettier taking >60s on large codebases).

Solution: Adopt unified biome.json replacing both:

{
  "$schema": "https://biomejs.dev/schemas/1.9.0/schema.json",
  "organizeImports": { "enabled": true },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "correctness": { "noUnusedVariables": "error" }
    }
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 100
  }
}

Best Practices

Do:

• Target Biome 1.9+ as a unified linter, formatter, and import-sorter to eliminate multiple competing tools.
• Run biome ci . in CI pipelines to enforce formatting and lint rules in a fraction of a second.
• Enable useIgnoreFile: true so Biome automatically respects your .gitignore rules.
• Install the official Biome VS Code / Neovim extension for instant formatting on save.

Don't:

• Run Prettier and Biome simultaneously on the same files; they will conflict.
• Use --unsafe autofix flags in automated CI jobs without human review.
• Ignore schema validation; keep $schema set in biome.json for IDE autocomplete.

Troubleshooting

References

• Biome Documentation