EnvGuard

Type-safe environment variable validation for Node.js, Bun, and other JavaScript runtimes.

Features

• Type-safe: Full TypeScript support with automatic type inference
• Zero dependencies: Lightweight with no external dependencies
• Comprehensive validators: Built-in validators for strings, numbers, booleans, emails, URLs, UUIDs, durations, byte sizes, and more
• Custom validators: Easy to create your own validators
• Secret masking: Automatically mask sensitive values in error messages
• Flexible defaults: Support for default, devDefault, and testDefault values
• Conditional requirements: Make variables required based on other values
• Warning mode: Non-blocking validation for optional variables
• Extra variable detection: Warn or error on unknown environment variables
• Immutable output: Validated environment is frozen and protected
• .env.example generation: Auto-generate example files from your schema
• Colored error output: Beautiful, readable error messages

Installation

npm install envguard

Quick Start

import { cleanEnv, str, num, bool, email, url } from 'envguard';

const env = cleanEnv({
  PORT: num({ default: 3000 }),
  HOST: str({ default: 'localhost' }),
  DATABASE_URL: url(),
  API_KEY: str({ secret: true }),
  DEBUG: bool({ default: false }),
  ADMIN_EMAIL: email({ default: 'admin@example.com' }),
});

// Fully typed!
console.log(env.PORT);        // number
console.log(env.HOST);        // string
console.log(env.DATABASE_URL); // string
console.log(env.DEBUG);       // boolean

// Environment helpers
console.log(env.isProduction);  // boolean
console.log(env.isDevelopment); // boolean
console.log(env.isTest);        // boolean

Validators

Basic Validators

str(options?)

Validates string values.

import { str } from 'envguard';

const env = cleanEnv({
  // Basic string
  NAME: str(),
  
  // With default
  HOST: str({ default: 'localhost' }),
  
  // With validation
  CODE: str({ 
    minLength: 3,
    maxLength: 10,
    pattern: /^[A-Z]+$/,
  }),
  
  // With transformation
  SLUG: str({ 
    trim: true,
    toLowerCase: true,
  }),
  
  // With choices
  NODE_ENV: str({ 
    choices: ['development', 'staging', 'production'],
  }),
});

num(options?)

Validates numeric values.

import { num } from 'envguard';

const env = cleanEnv({
  PORT: num({ default: 3000 }),
  
  // With constraints
  MAX_CONNECTIONS: num({ 
    min: 1,
    max: 100,
    integer: true,
  }),
  
  // With choices
  RETRY_COUNT: num({ 
    choices: [1, 3, 5, 10],
  }),
});

bool(options?)

Validates boolean values. Accepts: 1, 0, true, false, yes, no, on, off, t, f, y, n.

import { bool } from 'envguard';

const env = cleanEnv({
  DEBUG: bool({ default: false }),
  ENABLE_CACHE: bool({ default: true }),
});

Network Validators

email(options?)

Validates email addresses.

import { email } from 'envguard';

const env = cleanEnv({
  ADMIN_EMAIL: email(),
  SUPPORT_EMAIL: email({ default: 'support@example.com' }),
});

url(options?)

Validates URLs with http/https protocol.

import { url } from 'envguard';

const env = cleanEnv({
  API_URL: url(),
  WEBHOOK_URL: url({ default: 'https://example.com/webhook' }),
});

host(options?)

Validates hostnames or IP addresses (IPv4 and IPv6).

import { host } from 'envguard';

const env = cleanEnv({
  DB_HOST: host({ default: 'localhost' }),
  REDIS_HOST: host(),
});

port(options?)

Validates TCP port numbers (1-65535).

import { port } from 'envguard';

const env = cleanEnv({
  PORT: port({ default: 3000 }),
  
  // Custom range
  ADMIN_PORT: port({ min: 1024, max: 49151 }),
});

Data Validators

json<T>(options?)

Parses JSON values.

import { json } from 'envguard';

const env = cleanEnv({
  CONFIG: json<{ key: string }>(),
  
  // With schema validation
  SETTINGS: json<Settings>({
    schema: (v): v is Settings => 
      typeof v === 'object' && v !== null && 'name' in v,
  }),
});

array<T>(options?)

Parses comma-separated values into arrays.

import { array, num } from 'envguard';

const env = cleanEnv({
  // String array
  ALLOWED_HOSTS: array({ default: ['localhost'] }),
  
  // Custom separator
  TAGS: array({ separator: '|' }),
  
  // With item validation
  PORTS: array({ itemValidator: num() }),
  
  // With constraints
  IDS: array({ 
    minItems: 1,
    maxItems: 10,
    unique: true,
  }),
});

uuid(options?)

Validates UUID strings.

import { uuid } from 'envguard';

const env = cleanEnv({
  SESSION_ID: uuid(),
  TENANT_ID: uuid({ default: '00000000-0000-0000-0000-000000000000' }),
});

Special Validators

enums(options)

Validates against a list of allowed values with proper TypeScript inference.

import { enums } from 'envguard';

const env = cleanEnv({
  LOG_LEVEL: enums({ 
    values: ['debug', 'info', 'warn', 'error'] as const,
    default: 'info',
  }),
});

// env.LOG_LEVEL is typed as 'debug' | 'info' | 'warn' | 'error'

regex(options)

Validates against a custom regular expression.

import { regex } from 'envguard';

const env = cleanEnv({
  LICENSE_KEY: regex({ 
    pattern: /^[A-Z]{3}-\d{4}-[A-Z]{3}$/,
    desc: 'License key in format XXX-0000-XXX',
  }),
});

duration(options?)

Parses duration strings (e.g., 100ms, 5s, 2m, 1h, 7d).

import { duration } from 'envguard';

const env = cleanEnv({
  // Returns milliseconds by default
  TIMEOUT: duration({ default: 5000 }),
  
  // Convert to seconds
  CACHE_TTL: duration({ unit: 's' }),
});

// TIMEOUT=30s -> 30000 (ms)
// CACHE_TTL=5m -> 300 (s)

bytes(options?)

Parses byte size strings (e.g., 100B, 5KB, 2MB, 1GB).

import { bytes } from 'envguard';

const env = cleanEnv({
  // Returns bytes by default
  MAX_FILE_SIZE: bytes({ default: 10485760 }), // 10MB
  
  // Convert to megabytes
  MEMORY_LIMIT: bytes({ unit: 'MB' }),
});

// MAX_FILE_SIZE=50MB -> 52428800 (bytes)
// MEMORY_LIMIT=2GB -> 2048 (MB)

Advanced Features

Default Values

EnvGuard supports multiple types of default values:

const env = cleanEnv({
  // Always use this default
  PORT: num({ default: 3000 }),
  
  // Only in non-production environments
  DEBUG: bool({ devDefault: true }),
  
  // Only in test environment
  DB_URL: str({ testDefault: 'sqlite::memory:' }),
});

Secret Masking

Mark sensitive variables to mask their values in error messages:

const env = cleanEnv({
  API_KEY: str({ secret: true }),
  DATABASE_PASSWORD: str({ secret: true }),
});

// Error messages will show: "API_KEY: supe**********d123"

Conditional Requirements

Make variables required based on other values:

const env = cleanEnv({
  USE_REDIS: bool({ default: false }),
  REDIS_URL: str({
    requiredWhen: (env) => env.USE_REDIS === true,
    default: undefined,
  }),
});

Warning Mode

Use warnOnly for non-critical variables that shouldn't block startup:

const env = cleanEnv({
  ANALYTICS_KEY: str({ 
    warnOnly: true,
    desc: 'Optional analytics tracking key',
  }),
});

Extra Variable Detection

Detect unknown environment variables:

const env = cleanEnv(
  { PORT: num() },
  {
    // Warn about extra variables
    warnOnExtra: true,
    
    // Or throw an error
    strict: true,
    
    // Allow specific extra variables
    allowedExtra: ['CUSTOM_VAR'],
  }
);

Custom Validators

Create your own validators:

import { makeValidator, EnvValidationError } from 'envguard';

const hexColor = makeValidator<string>((value, key) => {
  if (!/^#[0-9A-Fa-f]{6}$/.test(value)) {
    throw new EnvValidationError(key, 'must be a valid hex color', value);
  }
  return value.toLowerCase();
});

const env = cleanEnv({
  PRIMARY_COLOR: hexColor({ default: '#000000' }),
  ACCENT_COLOR: hexColor(),
});

Custom Middleware

Transform the validated environment:

import { customCleanEnv, str, num } from 'envguard';

const env = customCleanEnv(
  {
    DB_HOST: str({ default: 'localhost' }),
    DB_PORT: num({ default: 5432 }),
    DB_NAME: str(),
  },
  (env) => ({
    ...env,
    connectionString: `postgres://${env.DB_HOST}:${env.DB_PORT}/${env.DB_NAME}`,
  })
);

console.log(env.connectionString);

Utility Functions

Group by Prefix

import { cleanEnv, str, num, groupByPrefix } from 'envguard';

const env = cleanEnv({
  DB_HOST: str({ default: 'localhost' }),
  DB_PORT: num({ default: 5432 }),
  DB_NAME: str({ default: 'mydb' }),
  CACHE_HOST: str({ default: 'localhost' }),
});

const dbConfig = groupByPrefix(env, 'DB');
// { host: 'localhost', port: 5432, name: 'mydb' }

Generate .env.example

import { writeEnvExample, str, num, bool } from 'envguard';

const spec = {
  PORT: num({ default: 3000, desc: 'Server port' }),
  HOST: str({ desc: 'Server host', example: 'localhost' }),
  DEBUG: bool({ default: false, desc: 'Enable debug mode' }),
  API_KEY: str({ desc: 'API key for external service', secret: true }),
};

writeEnvExample(spec, {
  outputPath: '.env.example',
  includeDescriptions: true,
  includeExamples: true,
  groupByPrefix: true,
});

Output:

# Server port
PORT=3000
# Server host
HOST=localhost
# Enable debug mode
DEBUG=false
# API key for external service
API_KEY= # Required

Custom Reporter

Override error handling:

import { cleanEnv, str } from 'envguard';

const env = cleanEnv(
  { API_KEY: str() },
  {
    reporter: {
      onError: (errors) => {
        // Custom error handling
        console.error('Config errors:', errors);
        process.exit(1);
      },
      onWarning: (warnings) => {
        // Custom warning handling
        console.warn('Config warnings:', warnings);
      },
    },
  }
);

API Reference

cleanEnv(spec, options?)

Main validation function.

Options:

• env: Custom environment object (default: process.env)
• reporter: Custom error reporter
• strict: Throw on unknown variables (default: false)
• warnOnExtra: Warn on unknown variables (default: false)
• allowedExtra: Array of allowed extra variable names

Validator Options

All validators accept these common options:

• default: Default value when variable is missing
• devDefault: Default for non-production environments
• testDefault: Default for test environment only
• choices: Array of allowed values
• desc: Description for documentation
• example: Example value for .env.example
• docs: URL to documentation
• secret: Mask value in error messages
• deprecated: Deprecation warning message
• requiredWhen: Function to determine if required
• warnOnly: Don't fail on validation errors

License

MIT