HTTP Status Code

101 Switching Protocols

Informational

The server is switching protocols as requested by the client.

HTTP status code reference, response example, common causes, fixes, and related status codes.

What does HTTP 101 Switching Protocols mean?

HTTP 101 Switching Protocols is a status code sent by a server to indicate the result of an HTTP request.

Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.

In practice, HTTP 101 Switching Protocols usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.

Response example

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

HTTP example

HTTP/1.1 101 Switching Protocols

Relevant headers

Upgrade

Upgrade: websocket

Connection

Connection: Upgrade

Common causes

WebSocket handshake
Protocol upgrade request
HTTP connection upgraded to another protocol

How to fix it

Ensure Upgrade and Connection headers are correct
Verify the server supports the requested protocol

Common mistakes

Assuming the status code alone explains the full backend issue
Ignoring related response headers that add important context
Treating temporary errors as permanent failures
Retrying too aggressively without checking the cause
Debugging the frontend only when the problem is server-side

How browsers and APIs use it

Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.

Developer note

This status is common when opening WebSocket connections. If the upgrade fails, check reverse proxy settings and required headers.

Related status codes

HTTP 100 HTTP 426