Environment variables

Edit variables

1. Project Environment tab → Add variable, enter KEY and value (eye icon shows or hides values).
2. Save ("Redeploy for the app to pick them up").
3. General tab → Deploy.

• Names: letters, digits, underscores, not starting with a digit (e.g. DATABASE_URL); each name once.
• Values are stored exactly as typed; don't add quotes unless they're part of the value.
• Saving replaces the whole list with what's on screen. Unsaved edits trigger a warning if you leave.
• Editing needs the Developer role or higher.

When changes apply

Variables are applied when a container is created: every Deploy, Rebuild or rollback. Reload keeps the old variables.

Runtime only

Variables are not available during the build (Nixpacks, docker build, Buildpacks). This affects:

• build-time framework variables (NEXT_PUBLIC_*, VITE_*, REACT_APP_*),
• build steps needing secrets (private registry tokens).

Put non-secret build values in nixpacks.toml ([variables]) or the Dockerfile, or build in CI and use Deploy from Image. For Compose projects, variables go into a .env beside the compose file (${VAR} or env_file: .env).

PORT

Unset PORT defaults to 3000. Your app must listen on 0.0.0.0:$PORT. Set it for images with a fixed port (e.g. PORT=80 for nginx). See Ports and health checks.

Connecting a database

Copy the Connection URL under Connect your deployed apps (private network) on the database page, add it as DATABASE_URL (or REDIS_URL, MONGODB_URI…), and deploy.

Privacy

MarvX Assistant and the AI build debugger never see variable values (the debugger sees names only). Preview deployments reuse production variables.

API

GET /v1/apps/{id}/env lists variables. PUT /v1/apps/{id}/env with {"vars": [{"key": "PORT", "value": "3000"}]} replaces the list: anything omitted is deleted. Use a personal token (API tokens).