HTTP 101 Switching Protocols

In short: The server switches to the protocol requested by the client, for example WebSocket.

In more detail: The client sends Upgrade: websocket and Connection: Upgrade. If the server agrees it answers 101, and from then on the new protocol runs over the same connection instead of HTTP.

In Depth

When it occurs

• Setting up a WebSocket connection (chat, live data).
• Switching from HTTP/1.1 to another protocol via Upgrade.

What you can do

1. As a visitor there is nothing to do.
2. Operators: if WebSockets fail, check whether proxy, load balancer or CDN pass the Upgrade headers through.

See also: HTTP Status Codes Overview, HTTP