.env File Validator & Linter

EnvLint is a free browser-based validator for .env files — the environment variable configuration files used by nearly every modern web application. Paste your .env file into the editor above and instantly see a full parse of every key-value pair, a list of issues, and a generated .env.example template you can safely commit to your repository.

Unlike other online .env tools, EnvLint runs entirely in your browser. Your environment variables never leave your machine. There is no server, no database, and no network request. You can verify this by opening your browser's developer tools and watching the Network tab — you'll see nothing sent after you click "lint .env."

What EnvLint checks

• Missing values — keys with an equals sign but no value (e.g., API_KEY=)
• Duplicate keys — the same key appearing more than once; later values silently overwrite earlier ones
• Invalid line format — lines that aren't comments, blank lines, or valid KEY=VALUE pairs
• Exposed-looking secrets — keys whose names suggest sensitive data (SECRET, TOKEN, KEY, PASSWORD, PRIVATE) with real non-placeholder values
• Suspicious placeholders — common placeholder patterns (your-key-here, changeme, xxx) that suggest the file isn't configured for the current environment

How to use the .env.example output

The generated .env.example replaces all values with descriptive placeholders while preserving comments and key names. This file is safe to commit to version control — it documents which environment variables your project requires without exposing any secrets. Team members clone the repo, copy .env.example to .env, and fill in their own values.

The .env file format

A .env file stores environment variables as KEY=VALUE pairs, one per line. Lines beginning with # are comments. Values can be quoted with single or double quotes to preserve whitespace or include special characters. The export prefix is optional and is stripped by most loaders. Empty lines are ignored.

The format is read at startup by dotenv (Node.js), python-dotenv (Python), dotenv-rails (Ruby/Rails), godotenv (Go), and dozens of other libraries. Despite its ubiquity, there is no single formal specification — parsers differ in edge cases around quoted values, multiline support, and whitespace handling. EnvLint follows the most widely-adopted conventions from the original Node.js dotenv package.

Security note

Your .env file typically contains database credentials, API keys, authentication secrets, and other sensitive values. Never paste it into a tool that submits data to a server unless you fully trust that server and its data handling practices. EnvLint is designed from the ground up to eliminate this risk — there is no server to trust.