HTTP 405 Method Not Allowed vs 503 Service Unavailable
HTTP 405 (Method Not Allowed) is a 4xx Client Error response, while 503 (Service Unavailable) is a 5xx Server Error response. 405 indicates that the HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods. In contrast, 503 means that the server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
Description
The HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
When You See It
When sending POST to a read-only endpoint, or DELETE to a non-deletable resource.
How to Fix
Check the Allow response header for supported methods. Use the correct HTTP method.
Description
The server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
When You See It
During maintenance windows, server overload, or when the application pool is exhausted.
How to Fix
Wait and retry. Check the Retry-After header. Scale up servers if it's a capacity issue.
Key Differences
405 is a 4xx Client Error response, while 503 is a 5xx Server Error response.
HTTP 405: The HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
HTTP 503: The server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
You encounter 405 when when sending POST to a read-only endpoint, or DELETE to a non-deletable resource.
You encounter 503 when during maintenance windows, server overload, or when the application pool is exhausted.
When to Use Which
For 405 (Method Not Allowed): Check the Allow response header for supported methods. Use the correct HTTP method. For 503 (Service Unavailable): Wait and retry. Check the Retry-After header. Scale up servers if it's a capacity issue.