HTTP 101 Switching Protocols — What It Means & How to Fix It

The HTTP 101 Switching Protocols status code indicates the server is switching to a different protocol as requested by the client via the Upgrade header. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: This status code is sent in response to a client request that includes an Upgrade header.. It is most commonly seen when upgrading from HTTP/1.1 to WebSocket connections.. The server agrees to switch protocols and the connection transitions immediately.. After this response, communication continues using the new protocol.. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Client requests a WebSocket connection upgrade via the Upgrade header.. Client requests an upgrade to HTTP/2 from HTTP/1.1.. Application protocols that require a protocol switch after initial handshake.. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Ensure the client correctly sends the Upgrade header with the desired protocol.. Verify the server supports the requested protocol upgrade.. Check that firewalls and proxies allow WebSocket or other upgraded protocol traffic.. Inspect the Connection and Upgrade response headers for correctness.. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our HTTP Status Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.