101 Switching Protocols

What it means

After a 101 response, the connection stops speaking HTTP/1.1 and continues in the new protocol.

Common causes

• A WebSocket handshake succeeded.
• The client requested an Upgrade the server supports.

How to fix it

1. No action is needed for successful WebSocket connections.
2. If WebSockets fail behind a proxy, allow the Upgrade and Connection headers.

Example response

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

Worked example

A client sends Expect: 100-continue before uploading a large request body. The server's interim response tells it to continue; the client still waits for the final response after sending the body.

How to read this response

1. Find the status line in your browser's Network panel, API client, or server access log.
2. Read the response body and headers shown above; headers such as Location, Allow, Retry-After, and WWW-Authenticate explain the next step.
3. Use the code's class to orient your diagnosis: informational, successful, redirected, request-related, or server-side.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

Frequently asked questions

What it means: HTTP 101

101 Switching Protocols: The server agrees to switch to the protocol requested in the Upgrade header, most often WebSocket.

Common causes: 101

A WebSocket handshake succeeded. The client requested an Upgrade the server supports.

How to fix it: HTTP 101

No action is needed for successful WebSocket connections. If WebSockets fail behind a proxy, allow the Upgrade and Connection headers.

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