HTTP 101 Switching Protocols vs 417 Expectation Failed
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 417 (Expectation Failed) 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, 417 means that the server cannot meet the requirements of the Expect header.
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 server cannot meet the requirements of the Expect header.
When You See It
When the server doesn't support Expect: 100-continue.
How to Fix
Remove the Expect header from your request.
Key Differences
101 is a 1xx Informational response, while 417 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 417: The server cannot meet the requirements of the Expect header.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 417 when when the server doesn't support Expect: 100-continue.
When to Use Which
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 417 (Expectation Failed): Remove the Expect header from your request.