HTTP 411 Length Required vs 426 Upgrade Required
Both HTTP 411 (Length Required) and 426 (Upgrade Required) belong to the 4xx Client Error category. 411 indicates that the server refuses to accept the request without a Content-Length header. Meanwhile, 426 means that the server refuses to perform the request using the current protocol but might after the client upgrades to a different protocol.
Description
The server refuses to accept the request without a Content-Length header.
When You See It
When sending a request body without specifying Content-Length.
How to Fix
Include a Content-Length header in your request.
Description
The server refuses to perform the request using the current protocol but might after the client upgrades to a different protocol.
When You See It
When a server requires HTTPS or a newer protocol version.
How to Fix
Switch to the protocol specified in the Upgrade response header.
Key Differences
HTTP 411: The server refuses to accept the request without a Content-Length header.
HTTP 426: The server refuses to perform the request using the current protocol but might after the client upgrades to a different protocol.
You encounter 411 when when sending a request body without specifying Content-Length.
You encounter 426 when when a server requires HTTPS or a newer protocol version.
When to Use Which
For 411 (Length Required): Include a Content-Length header in your request. For 426 (Upgrade Required): Switch to the protocol specified in the Upgrade response header.