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

The 101 (Switching Protocols) status code indicates that the server understands and is willing to comply with the client's request to switch to a different protocol. This is typically used in response to an Upgrade header field in a client request, signifying a protocol change for the current connection.

Last updated: 2026-06-11

RECOMMENDED

Essential Reading: Designing Data-Intensive Applications

The system design bible for software engineers. Learn to build reliable, scalable, and maintainable systems.

View on Amazon →

                Status Code
                101
            

Name Switching Protocols

Common Causes

Client explicitly requests a protocol upgrade (e.g., from HTTP/1.1 to WebSockets).
Server agrees to the client's requested protocol switch.
During the initial handshake for protocols like WebSockets.

Code Examples to Handle HTTP 101

curl -I https://httpbin.org/status/101

fetch('https://httpbin.org/status/101')
  .then(response => {
    if (response.status === 101) {
      console.log('Handled Switching Protocols');
    }
  });

import requests

response = requests.get('https://httpbin.org/status/101')
if response.status_code == 101:
    print("Received Switching Protocols")

How to Fix It

Verify that the client's 'Upgrade' header specifies a protocol that the server supports and is configured to handle.
Ensure the server's application logic correctly processes the 'Upgrade' header and initiates the protocol switch.
Check server logs for any errors related to protocol negotiation or the upgrade process.

💡 Example: A web browser wants to establish a WebSocket connection with a server. It sends an HTTP GET request with an 'Upgrade: websocket' and 'Connection: Upgrade' header. The server, upon receiving this, responds with a 101 Switching Protocols status, indicating it's now switching the connection to the WebSocket protocol.

🛠️ Developer Tip: When implementing protocol upgrades, ensure both client and server correctly handle the 'Upgrade' and 'Connection' headers. Focus on robust error handling during the handshake phase for new protocols.

Related Status Codes

Frequently Asked Questions

What causes HTTP 101?

HTTP 101 is caused when a client requests to switch protocols (e.g., to WebSockets) using the 'Upgrade' header, and the server agrees to perform that switch for the current connection.

How do I fix HTTP 101?

HTTP 101 is generally not an error but an informational status. If you're encountering issues, ensure your client is requesting a supported protocol and that your server is correctly configured to handle the 'Upgrade' header and initiate the new protocol.