# Unable to call Edge Function

If you're having trouble invoking an Edge Function or experiencing CORS issues, follow these steps to diagnose and resolve the problem.

## Diagnose the issue

1. **Review CORS configuration:** Check out the [CORS guide](https://supabase.com/docs/guides/functions/cors) and ensure you've properly configured CORS headers
2. **Check function logs:** Look for errors in Functions > Logs in the dashboard
3. **Verify authentication:** Confirm JWT tokens and permissions are correct

## Proper CORS handling

Make sure your function handles OPTIONS preflight requests.

### Recommended (v2.95.0+)

Note: **For `@supabase/supabase-js` v2.95.0 and later:** Import CORS headers directly from the SDK to ensure they stay synchronized with any new headers added to the client libraries.

```tsx
// Recommended approach
import { corsHeaders } from '@supabase/supabase-js/cors' // v2.95.0+

Deno.serve(async (req) => {
  if (req.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders })
  }

  // Your function logic here
  return new Response(JSON.stringify({ status: 'Success' }), {
    headers: { ...corsHeaders, 'Content-Type': 'application/json' },
  })
})
```

### For versions before 2.95.0

If you're using `@supabase/supabase-js` before v2.95.0, you'll need to hardcode the CORS headers. Add a `cors.ts` file within a [`_shared` folder](https://supabase.com/docs/guides/functions/quickstart#organizing-your-edge-functions):

```ts
// _shared/cors.ts
export const corsHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Headers': 'authorization, x-client-info, apikey, content-type',
}
```

Then import it in your function:

```tsx
import { corsHeaders } from '../_shared/cors.ts'

Deno.serve(async (req) => {
  // Handle CORS preflight requests
  if (req.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders })
  }

  // Your function logic here
  return new Response(JSON.stringify({ status: 'Success' }), {
    headers: { ...corsHeaders, 'Content-Type': 'application/json' },
  })
})
```

## Debugging tools

Supabase provides two debugging tools for Edge Functions:

- **Invocations:** Shows the Request and Response for each execution
- **Logs:** Shows platform events, including deployments and errors

Access these tools by navigating to Functions > \[Your Function] in the dashboard.

## Common issues

### CORS errors

- Missing `Access-Control-Allow-Origin` header in response
- Not handling OPTIONS preflight requests
- Mismatched allowed methods or headers

### Authentication errors

- Invalid or expired JWT token
- Missing Authorization header
- Incorrect permissions for the authenticated user

### Network errors

- Function not deployed
- Incorrect function URL
- Network connectivity issues

## Additional resources

- [CORS guide](https://supabase.com/docs/guides/functions/cors)
- [Edge Functions authentication](https://supabase.com/docs/guides/functions/auth)
- [Debugging Edge Functions](https://supabase.com/docs/guides/functions/logging)