A .env (environment) file stores configuration variables as key-value pairs, typically used to manage settings across different environments (development, staging, production). It keeps sensitive data like API keys and database credentials out of source code, following the 12-Factor App methodology.

Nested JSON objects are flattened by joining parent and child keys with a separator (default: underscore). For example, {"db": {"host": "localhost"}} becomes DB_HOST=localhost. You can customize the separator to double underscore (__) or dot notation (.) depending on your framework's conventions.

You have two options: Indexed mode expands each array element into separate keys (e.g., FEATURES_0=auth, FEATURES_1=logging), while Comma mode joins all elements into a single comma-separated value (e.g., FEATURES=auth,logging,caching). Choose based on how your application parses the environment variable.

Yes! Click the Swap button to reverse the conversion direction. The tool intelligently detects nested keys (based on the separator pattern) and reconstructs the original JSON structure. Type inference can also detect booleans, numbers, and null values automatically.

Values containing spaces, equals signs (=), hash symbols (#), double quotes, or leading/trailing whitespace are automatically wrapped in double quotes. Internal double quotes are escaped with backslashes. This ensures compatibility with all major .env parsers including dotenv (Node.js), python-dotenv, and direnv.

Absolutely. All conversion happens entirely in your browser using client-side JavaScript. Your JSON or .env data never leaves your device — no data is sent to any server, ensuring your sensitive credentials and API keys remain completely private.