1xx Informational

101 Switching Protocols

The server is switching to the protocol the client asked for in the Upgrade header.

Most often seen when a WebSocket connection is established: the HTTP request is upgraded and the connection then speaks the WebSocket protocol.

Notes

• If a WebSocket handshake fails behind nginx, make sure proxy_set_header Upgrade $http_upgrade; and Connection "upgrade" are configured and proxy_http_version 1.1 is set.

Example response

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Date: Thu, 22 Oct 2026 08:00:00 GMT

Check a URL’s status with curl -I https://example.com, which prints the status line and headers.

Related status codes

• 100 Continue

Related tools

curl to Code · LLM API Playground · LLM Stream Parser