How to Troubleshoot CORS Issues in API Gateway

If you encounter CORS (Cross-Origin Resource Sharing) errors when making API requests, there are several common causes and solutions to check:

Common CORS Error Messages

• "No 'Access-Control-Allow-Origin' header is present on the requested resource"

• "Request header field is not allowed by Access-Control-Allow-Headers in preflight response"

Troubleshooting Steps

1. Clear Browser Cache - First try clearing your browser cache as CORS settings may be cached locally.

2. Verify API Gateway CORS Configuration - Ensure your API Gateway CORS settings include:

   • Correct origin domains in Access-Control-Allow-Origin

   • All required custom headers in Access-Control-Allow-Headers (e.g., x-tenant-id)

3. Check Deployment Status - After making changes to API Gateway configurations:

   • Ensure you redeploy the API Gateway for changes to take effect

   • Verify the correct branch/configuration is deployed to your environment

4. Environment Testing - When making CORS configuration changes:

   • Test changes in development environment first

   • Only promote to other environments (sandbox, production) after successful testing