HTTP 100 Continue vs 101 Switching Protocols
Both HTTP 100 (Continue) and 101 (Switching Protocols) belong to the 1xx Informational category. 100 indicates that the server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected. Meanwhile, 101 means that the server understands the Upgrade header field request and indicates which protocol it is switching to.
説明
The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
このコードが表示される場合
When a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
解決方法
This is an interim response — no fix needed. The client should continue sending the request body.
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.
主な違い
HTTP 100: The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
You encounter 100 when when a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
どちらをいつ使うか
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.