# Troubleshooting error response status codes in CloudFront
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If CloudFront requests an object from your origin, and the origin returns an HTTP 4xx or 5xx status code, there's a problem with communication between CloudFront and your origin. 

This topic also includes troubleshooting steps for these status codes when using Lambda@Edge or CloudFront Functions.

The following topics provide detailed explanations of the potential causes behind these error responses and offers step-by-step guidance on how to diagnose and resolve the underlying issues.

**Topics**
+ [HTTP 400 status code (Bad Request)](http-400-bad-request.md)
+ [HTTP 401 status code (Unauthorized)](http-401-unauthorized.md)
+ [HTTP 403 status code (Invalid method)](http-403-invalid-method.md)
+ [HTTP 403 status code (Permission Denied)](http-403-permission-denied.md)
+ [HTTP 404 status code (Not Found)](http-404-not-found.md)
+ [HTTP 412 status code (Precondition Failed)](http-412-precondition-failed.md)
+ [HTTP 500 status code (Internal Server Error)](http-500-internal-server-error.md)
+ [HTTP 502 status code (Bad Gateway)](http-502-bad-gateway.md)
+ [HTTP 503 status code (Service Unavailable)](http-503-service-unavailable.md)
+ [HTTP 504 status code (Gateway Timeout)](http-504-gateway-timeout.md)