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.
Descripción
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.
Cuándo lo verás
When a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
Cómo solucionarlo
This is an interim response — no fix needed. The client should continue sending the request body.
Descripción
The server understands the Upgrade header field request and indicates which protocol it is switching to.
Cuándo lo verás
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
Cómo solucionarlo
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
Diferencias clave
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.
Cuándo usar cada uno
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.