Formatter

Biome is an opinionated formatter that supports multiple languages. It follows a similar philosophy to Prettier, only supporting a few options to avoid debates over styles, turning into debates over Biome options. It deliberately resists the urge to add new options to prevent bike-shed discussions in teams so they can focus on what really matters instead.

CLI

Section titled CLI

The following command checks the formatting of the files in the src directory. It emits text differences if it finds code that is not formatted.

npm

npx @biomejs/biome format ./src

yarn

yarn biome format ./src

pnpm

pnpm biome format ./src

bun

bunx @biomejs/biome format ./src

deno

deno run -A npm:@biomejs/biome format ./src

If you want to apply the new formatting, pass the --write option:

npm

npx @biomejs/biome format --write ./src

yarn

yarn biome format --write ./src

pnpm

pnpm biome format --write ./src

bun

bunx @biomejs/biome format --write ./src

deno

deno run -A npm:@biomejs/biome format --write ./src

The command accepts a list of files and directories.

Caution

If you pass a glob as a parameter, your shell will expand it. The result of the expansion depends on your shell. For example, some shells don’t support the recursive glob ** or the alternation {} in the following command:

biome format ./src/**/*.test.{js,ts}

Shell expansion has a performance cost and a limit on the number of files you can pass to the command.

For more information about all the available options, check the CLI reference.

Options

Section titled Options

Biome provides some options to tune the behavior of its formatter. Differently from other tools, Biome separates language-agnostic options from language-specific options.

The formatter options can be set on the CLI or in the biome.json configuration file. Biome doesn’t support .editorconfig yet.

It’s recommended to use the configuration file to ensure that both the Biome CLI and the Biome LSP apply the same options. The following defaults are applied:

biome.json

{
  "formatter": {
    "enabled": true,
    "formatWithErrors": false,
    "ignore": [],
    "attributePosition": "auto",
    "indentStyle": "tab",
    "indentWidth": 2,
    "lineEnding": "lf",
    "lineWidth": 80
  },
  "javascript": {
    "formatter": {
      "arrowParentheses":"always",
      "bracketSameLine": false,
      "bracketSpacing": true,
      "jsxQuoteStyle": "double",
      "quoteProperties": "asNeeded",
      "semicolons": "always",
      "trailingComma": "all"
    }
  },
  "json": {
    "formatter": {
      "trailingCommas": "none"
    }
  }
}

The main language-agnostic options supported by the Biome formatter are:

• indent style (default: tab): Use spaces or tabs for indention;
• line width (default: 80): The column width at which Biome wraps code;
• tab width (default: 2): The number of spaces per indention level.

See the configuration reference for more details.

Ignoring Code

Section titled Ignoring Code

There are times when the formatted code isn’t ideal.

For these cases, you can use a format suppression comment:

example.js

// biome-ignore format: <explanation>

Example:

example.js

const expr =
  // biome-ignore format: the array should not be formatted
  [
    (2 * n) / (r - l),
    0,
    (r + l) / (r - l),
    0,
    0,
    (2 * n) / (t - b),
    (t + b) / (t - b),
    0,
    0,
    0,
    -(f + n) / (f - n),
    -(2 * f * n) / (f - n),
    0,
    0,
    -1,
    0,
  ];

Ignoring files

Section titled Ignoring files

Biome doesn’t provide ignore comments that ignore an entire file. However, you can ignore a file using the Biome configuration file.

You can ignore files for all tools, including the formatter, using the files.ignore configuration. By default, Biome ignores the protected files.

If you want to exclude files from being formatted, you can use formatter.ignore:

biome.jsonc

{
  "files": {
    // All tools, including the formatter, ignore following files
    "ignore": ["dist/**"]
  },
  "formatter": {
    // Only the formatter ignores the following files
    "ignore": ["test/**"]
  }
}

Note that you can also ignore files ignored by your VCS.