HTTP 101 Switching Protocols vs 303 See Other
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 303 (See Other) is a 3xx Redirection response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 303 means that the server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern).
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.
Descripción
The server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern).
Cuándo lo verás
After form submissions to prevent resubmission on browser refresh.
Cómo solucionarlo
Follow the Location header with a GET request. This is intentional — part of the PRG pattern.
Diferencias clave
101 is a 1xx Informational response, while 303 is a 3xx Redirection response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 303: The server is redirecting to a different resource using GET, typically after a POST operation (Post/Redirect/Get pattern).
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 303 when after form submissions to prevent resubmission on browser refresh.
Cuándo usar cada uno
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 303 (See Other): Follow the Location header with a GET request. This is intentional — part of the PRG pattern.