HTTP 101 Switching Protocols vs 405 Method Not Allowed
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 405 (Method Not Allowed) is a 4xx Client Error response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 405 means that the HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
Description
The server understands the Upgrade header field request and indicates which protocol it is switching to.
When You See It
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
How to Fix
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
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.
Key Differences
101 is a 1xx Informational response, while 405 is a 4xx Client Error response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 405: The HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 405 when when sending POST to a read-only endpoint, or DELETE to a non-deletable resource.
When to Use Which
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 405 (Method Not Allowed): Check the Allow response header for supported methods. Use the correct HTTP method.