.env.development.local May 2026

You are working on a team project that uses a third-party API (like Stripe or Google Maps).

Assuming you are running your app in development mode (e.g., npm start or next dev), the system looks for environment files in the following priority order (lowest to highest, where highest wins): .env.development.local

Crucial Rule: Later files override earlier files. If the same variable exists in .env and .env.development.local, the value in .env.development.local takes precedence. You are working on a team project that

Remember that CRA (React) requires REACT_APP_, Vite requires VITE_, and Next.js exposes all by default. Using the wrong prefix is the #1 reason environment variables appear undefined. Crucial Rule: Later files override earlier files

Next.js supports environment files but with a twist. It supports .env.development and .env.local, but officially .env.development.local is not a documented file. Next.js recommends using .env.local for all local overrides, regardless of mode. Always check your framework's documentation, as this behavior is not universal.

# .env.production.local (Ignored)
NODE_OPTIONS="--inspect"
LOG_LEVEL="debug"

Run your production build locally with debugging enabled, without altering the production config.