HTTP 101 Switching Protocols

What does HTTP 101 mean?

The server agrees to switch to the protocol named in the client’s Upgrade header. You see 101 in DevTools when a WebSocket connection is opened: the HTTP/1.1 request carries Upgrade: websocket, and after the 101 the connection carries WebSocket frames instead of HTTP.

1xx Informational: The request was received and processing continues. Browsers handle these automatically; you rarely see them in DevTools.

When you see 101

• A WebSocket handshake succeeded (normal).
• A proxy without WebSocket support may break the upgrade and return 400 or 502 instead.

101 and SEO

No SEO impact.

Example response

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade

Related status codes

• 100 Continue — The server has received the request headers and the client may send the body.
• 426 Upgrade Required — The server requires the client to switch to a different protocol.
• 400 Bad Request — The server cannot process the request because it is malformed.

Check which status code a URL returns with the HTTP header checker.