Check if port 54321 is in use

If supabase functions serve fails or you're having trouble running Edge Functions locally, follow these steps to diagnose and resolve the issue.

Debugging steps

Use debug mode

Run the serve command with the --debug flag for detailed output:

supabase functions serve your-function --debug

Check port availability

Ensure the required ports are available. The Supabase CLI uses ports 54321 and 8081 by default:

# Check if port 54321 is in use
lsof -i :54321

# Check if port 8081 is in use
lsof -i :8081

If these ports are in use, stop the processes using them or configure different ports.

Common issues

Port conflicts

Another process may be using the required ports. Check for:

• Other Supabase projects running locally
• Docker containers
• Other development servers

Deno cache issues

Clear the Deno cache if you're experiencing module resolution problems:

deno cache --reload /path/to/function/index.ts

Environment variables

Make sure your .env file is properly configured and accessible to the CLI.

Getting more help

If the problem persists, search the following repositories for similar error messages:

• Edge Runtime repository
• CLI repository

If the output from these commands does not help resolve the issue, open a support ticket via the Supabase Dashboard (by clicking the "Help" button at the top right) and include all output and details about your commands.

Additional resources

• Local development guide
• Edge Functions quickstart
• Debugging Edge Functions