101Switching Protocols
The server is agreeing to change protocol on this connection, almost always from HTTP to WebSocket.
Browse all HTTP status codesWhen you see it
This is the handshake that opens a WebSocket. The client sends an Upgrade header asking to switch, and 101 is the server saying yes. From that point the connection is no longer speaking HTTP, which is why you see 101 once at the start of a live connection and never again.
If a WebSocket connection is failing and you never see a 101, the request is being blocked before it reaches the application. A proxy or load balancer that does not forward the Upgrade header is the usual cause.
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Status codes
69 of 69 codes. Click a row to copy it.
1xx Informational (4)
2xx Success (10)
3xx Redirection (8)
4xx Client errors (31)
5xx Server errors (16)