Environment Variables

Environment variables that control and influence Biome's behavior.

Capabilities

Biome-Specific Variables

Environment variables specific to Biome configuration and operation.

BIOME_CONFIG_PATH

Path to the Biome configuration file.

BIOME_CONFIG_PATH=<PATH>

Type: String (file path)

Usage:

# Set configuration path
export BIOME_CONFIG_PATH=/path/to/biome.json
biome check

# Per-command
BIOME_CONFIG_PATH=./configs/biome.json biome check --write

Behavior:

• Alternative to --config-path CLI option
• CLI option takes precedence over environment variable
• Disables default configuration file discovery
• Can point to file or directory containing biome.json/biome.jsonc

BIOME_BINARY

Override path to the native Biome binary.

BIOME_BINARY=<PATH>

Type: String (file path)

Usage:

# Use custom binary
export BIOME_BINARY=/path/to/custom/biome
biome check

# Use locally built binary
export BIOME_BINARY=./target/release/biome
biome check

Behavior:

• Overrides automatic platform detection and binary resolution
• Used by the Node.js wrapper to locate the native executable
• Useful for:
  • Testing custom builds
  • Using binaries on unsupported platforms
  • Development and debugging

BIOME_LOG_PATH

Directory where daemon server logs are stored.

BIOME_LOG_PATH=<PATH>

Type: String (directory path)

Default: Platform-specific cache directory

• Linux: $XDG_CACHE_HOME/biome or ~/.cache/biome
• macOS: ~/Library/Caches/biome
• Windows: %LOCALAPPDATA%\biome\cache

Usage:

# Set log directory
export BIOME_LOG_PATH=/var/log/biome
biome start

# Per-command
BIOME_LOG_PATH=/tmp/biome-logs biome start

Behavior:

• Alternative to --log-path CLI option (for start and lsp-proxy commands)
• CLI option takes precedence over environment variable
• Directory is created if it doesn't exist
• Log files named with BIOME_LOG_PREFIX_NAME prefix

Related:

• BIOME_LOG_PREFIX_NAME - Log file name prefix
• --log-path CLI option

BIOME_LOG_PREFIX_NAME

Prefix for daemon log file names.

BIOME_LOG_PREFIX_NAME=<STRING>

Type: String

Default: "server.log"

Usage:

# Set log prefix
export BIOME_LOG_PREFIX_NAME=biome-daemon
biome start
# Creates: biome-daemon.{timestamp}.log

# Multiple instances
BIOME_LOG_PREFIX_NAME=instance-1 biome start
BIOME_LOG_PREFIX_NAME=instance-2 biome start

Behavior:

• Alternative to --log-prefix-name CLI option
• CLI option takes precedence over environment variable
• Useful for distinguishing logs from multiple daemon instances
• Full log filename: {prefix}.{timestamp}.log

BIOME_THREADS

Number of threads to use for parallel processing.

BIOME_THREADS=<NUMBER>

Type: Number (positive integer)

Default: Number of CPU cores

Usage:

# Limit threads in CI
export BIOME_THREADS=2
biome ci

# Single-threaded processing
BIOME_THREADS=1 biome check

# Use all cores explicitly
BIOME_THREADS=$(nproc) biome check

Behavior:

• Controls parallelism for file processing
• Useful in resource-limited CI environments
• Lower values reduce memory usage and CPU load
• Alternative to --threads CLI option (available in ci command)
• CLI option takes precedence over environment variable

Use Cases:

• CI environments with limited resources
• Containers with CPU limits
• Avoiding resource exhaustion in shared environments

BIOME_VERSION

Biome version string (build-time only).

BIOME_VERSION=<VERSION>

Type: String

Usage:

This variable is used during Biome's build process to embed version information. It's not intended for user configuration.

Behavior:

• Read during compilation/build only
• Not used at runtime
• Version displayed by biome version command

Standard Environment Variables

Standard environment variables that Biome reads and respects.

NO_COLOR

Disable colored output.

NO_COLOR=<any-value>

Type: Boolean (any value disables color)

Standard: NO_COLOR

Usage:

# Disable colors
export NO_COLOR=1
biome check

# Disable colors (any value works)
NO_COLOR=true biome check
NO_COLOR= biome check

Behavior:

• When set (to any value), disables ANSI color codes in output
• Overridden by --colors=force CLI option
• Standard convention respected by many CLI tools
• Useful for:
  • Log files
  • CI systems that don't support colors
  • Accessibility (screen readers)
  • Output piping and processing

TERM

Terminal type information.

TERM=<terminal-type>

Type: String

Common Values: xterm, xterm-256color, screen, dumb, vt100

Usage:

# Set terminal type
export TERM=xterm-256color
biome check

# Dumb terminal (no colors)
TERM=dumb biome check

Behavior:

• Read to determine terminal capabilities
• Influences color and formatting decisions
• dumb terminal type disables colors
• Automatically set by terminal emulators

GITHUB_ACTIONS

Detected by Biome to enable GitHub Actions-specific behavior.

GITHUB_ACTIONS=<true|false>

Type: String (typically "true" when running in GitHub Actions)

Usage:

Set automatically by GitHub Actions when workflows run. Not intended for manual configuration.

# Automatically set by GitHub Actions
GITHUB_ACTIONS=true

# Biome detects and adjusts behavior accordingly
biome ci --reporter=github

Behavior:

• Automatically set by GitHub Actions CI environment
• Biome detects this variable to optimize output for GitHub
• May influence reporting format and color handling
• Used for generating GitHub workflow annotations
• Helps Biome provide better integration with GitHub Actions workflows

Related:

• Use --reporter=github to generate GitHub Actions workflow commands
• GitHub-specific formatting for errors and warnings

Node.js Runtime Variables

Variables set by the Node.js wrapper and passed to the native binary for context.

JS_RUNTIME_VERSION

JavaScript runtime version.

JS_RUNTIME_VERSION=<version>

Type: String

Example: v20.10.0

Usage:

Set automatically by the Node.js wrapper based on process.version. Not intended for manual configuration.

Behavior:

• Passed to native binary for diagnostic information
• Included in biome rage output
• Useful for debugging runtime-specific issues

JS_RUNTIME_NAME

JavaScript runtime name.

JS_RUNTIME_NAME=<name>

Type: String

Example: node

Usage:

Set automatically by the Node.js wrapper based on process.release.name. Not intended for manual configuration.

Behavior:

• Passed to native binary for diagnostic information
• Included in biome rage output
• Distinguishes Node.js from other JavaScript runtimes (Deno, Bun, etc.)

NODE_PACKAGE_MANAGER

Package manager being used.

NODE_PACKAGE_MANAGER=<package-manager>

Type: String

Example: npm/8.19.2, pnpm/8.10.0, yarn/1.22.19

Usage:

Set automatically by package managers via npm_config_user_agent. Not intended for manual configuration.

Behavior:

• Detected from npm_config_user_agent environment variable
• Passed to native binary for diagnostic information
• Included in biome rage output
• Format: {name}/{version}

Environment Variable Precedence

When multiple configuration sources are available:

1. CLI options (highest precedence)
2. Environment variables
3. Configuration file
4. Default values (lowest precedence)

Example:

# Configuration file
{
  "files": {
    "maxSize": 1048576
  }
}

# Environment variable
export BIOME_CONFIG_PATH=/other/config.json

# CLI option overrides both
biome check --config-path=/final/config.json

Common Usage Patterns

CI/CD Environments

#!/bin/bash
# .gitlab-ci.yml or similar

export BIOME_THREADS=2
export NO_COLOR=1
export BIOME_CONFIG_PATH=./ci-config.json

biome ci --reporter=gitlab > gl-code-quality-report.json

Development Scripts

#!/bin/bash
# scripts/check-code.sh

export BIOME_CONFIG_PATH=./configs/biome.json
export BIOME_LOG_PATH=./logs

biome check --write --use-server

Docker Containers

# Dockerfile
FROM node:20

ENV BIOME_THREADS=2
ENV BIOME_CONFIG_PATH=/app/biome.json

WORKDIR /app
COPY . .
RUN npm install
RUN npx @biomejs/biome ci

Testing Custom Builds

#!/bin/bash
# Test locally built Biome binary

export BIOME_BINARY=./target/release/biome
export BIOME_LOG_LEVEL=debug
export BIOME_LOG_PATH=./debug-logs

biome check --write

Multiple Daemon Instances

# Instance 1
export BIOME_LOG_PREFIX_NAME=daemon-1
export BIOME_LOG_PATH=/tmp/biome/instance-1
biome start &

# Instance 2
export BIOME_LOG_PREFIX_NAME=daemon-2
export BIOME_LOG_PATH=/tmp/biome/instance-2
biome start &

Debugging with Environment Variables

For debugging and troubleshooting:

# Enable debug logging
export BIOME_LOG_PATH=./debug
biome start --log-level=debug

# Use server with debugging
export BIOME_THREADS=1  # Single-threaded for easier debugging
biome check --use-server --verbose --log-level=debug

# Check configuration resolution
export BIOME_CONFIG_PATH=./debug-config.json
biome rage --formatter --linter

Environment Variables in Scripts

Bash

#!/bin/bash
export BIOME_CONFIG_PATH=/path/to/config.json
export BIOME_THREADS=4
biome check --write

PowerShell

$env:BIOME_CONFIG_PATH = "C:\path\to\config.json"
$env:BIOME_THREADS = 4
biome check --write

npm/package.json Scripts

{
  "scripts": {
    "check": "BIOME_CONFIG_PATH=./configs/biome.json biome check --write",
    "ci": "BIOME_THREADS=2 NO_COLOR=1 biome ci --reporter=json"
  }
}

cross-env for Cross-Platform Scripts

{
  "scripts": {
    "check": "cross-env BIOME_CONFIG_PATH=./configs/biome.json biome check --write",
    "ci": "cross-env BIOME_THREADS=2 NO_COLOR=1 biome ci"
  }
}