101
Switching Protocols
1xx Informational
Class
RFC 9110 §15.2.2
Defined in
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: UpgradeRelated 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.
All HTTP status codesSearch the full list of status codes from 100 to 599 with their meanings and SEO impact.
Open the full list Frequently asked questions
What does status code 101 mean?
101 Switching Protocols: The server agrees to switch to the protocol named in the client’s
Upgrade header.Does 101 affect SEO?
No SEO impact.