101 Switching Protocols
The server agrees to switch the connection to a different protocol, such as upgrading from HTTP to WebSocket.
What it means
HTTP 101 Switching Protocols is sent in response to an Upgrade request header. The server acknowledges it will change the application protocol on this connection — most commonly upgrading an HTTP connection to the WebSocket protocol for real-time communication.
When it happens
It happens when a client requests a protocol upgrade — for example, a browser opening a WebSocket connection, or a client negotiating HTTP/2 over a cleartext connection.
How to fix it
- Nothing to fix — 101 indicates a successful, intentional protocol switch.
- If a WebSocket fails to open, verify the server, load balancer, and any proxies are configured to pass through Upgrade and Connection headers.
SEO impact
None. Protocol upgrades are unrelated to crawling and indexing of regular page content.
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Related codes
An interim response telling the client the initial part of a request was received and it should continue sending the body.
102 ProcessingA WebDAV interim response telling the client the server has accepted the request and is still working on it.
103 Early HintsAn interim response that lets the browser start fetching critical assets before the final page arrives.
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