HTTP 101 Switching Protocols vs 431 Request Header Fields Too Large
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 431 (Request Header Fields Too Large) 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, 431 means that the server refuses to process the request because an individual header field or all headers collectively are too large.
説明
The server understands the Upgrade header field request and indicates which protocol it is switching to.
このコードが表示される場合
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
解決方法
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
説明
The server refuses to process the request because an individual header field or all headers collectively are too large.
このコードが表示される場合
When cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
解決方法
Reduce header sizes. Clear excessive cookies. Use shorter tokens.
主な違い
101 is a 1xx Informational response, while 431 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 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 431 when when cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
どちらをいつ使うか
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.