HTTP 101 Switching Protocols

The server agrees to change the protocol used by the connection.

Use 101 for protocol upgrades such as a WebSocket handshake.

httpstatus codeinformationalwebsocket

Response (http)

HTTP/1.1 101 Switching Protocols

Use 101 for protocol upgrades such as a WebSocket handshake.

Common mistakes

Using 101 outside a negotiated Upgrade, or reusing the old protocol after switching.

Registry reference: RFC9110, Section 15.2.2

Sources