HTTP 101 Switching Protocols vs 428 Precondition Required
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 428 (Precondition Required) 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, 428 means that the server requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
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 requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
このコードが表示される場合
When an API requires optimistic concurrency control via ETags.
解決方法
Fetch the resource first to get its ETag, then include If-Match in your update request.
主な違い
101 is a 1xx Informational response, while 428 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 428: The server requires the request to be conditional (e.g., include If-Match header) to prevent lost updates.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 428 when when an API requires optimistic concurrency control via ETags.
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 428 (Precondition Required): Fetch the resource first to get its ETag, then include If-Match in your update request.