Skip to main content

​
Welcome to Env Core

Env Core is a lightweight, type-safe environment variable validation library for Node.js projects. It helps you catch configuration errors early by validating your environment variables at startup time.

Type-safe validation

Get full TypeScript type inference for your validated environment variables

Framework agnostic

Works seamlessly with Express.js, NestJS, and any Node.js framework

Detailed error messages

Clear, actionable error messages when validation fails

Zero configuration

Simple API with sensible defaults - works with .env files out of the box

​
Key features

  • Type-safe validation - Supports String, Number, and Boolean types with full TypeScript inference
  • Optional variables - Define optional variables with default values
  • Detailed errors - Get comprehensive error messages for missing or invalid variables
  • Framework compatible - Compatible with Express.js, NestJS, and other Node.js frameworks
  • Minimal dependencies - Only depends on dotenv for .env file parsing
  • ESM and CommonJS - Works with both import and require

​
How it works

Env Core validates your environment variables against a schema you define. If validation fails, your application won’t start, preventing runtime errors caused by misconfiguration. 
import { validateEnv } from 'env-core';

const env = validateEnv({
  PORT: Number,
  NODE_ENV: String,
  DEBUG: { type: Boolean, default: false }
});

// TypeScript knows the exact types!
console.log(env.PORT); // number
console.log(env.NODE_ENV); // string
console.log(env.DEBUG); // boolean

​
Quick navigation

Get started

Install Env Core and set up your first validation schema

Quick start

Follow a step-by-step guide to validate your first environment

Core concepts

Learn about schema definition, validation, and type safety

Framework guides

Integration guides for Express.js, NestJS, and more

​
Why Env Core?

Environment variables are a common source of runtime errors in Node.js applications. A missing or incorrectly typed variable can cause your application to crash in production. Env Core solves this by:
  • Validating at startup - Catch configuration errors before they cause problems
  • Providing type safety - TypeScript knows the exact types of your environment variables
  • Clear error messages - Quickly identify and fix configuration issues
  • Simple API - Define your schema and let Env Core handle the rest
Env Core is MIT licensed and open source. Contributions are welcome!

Build docs developers (and LLMs) love

Get started for freeTalk to us