HTTP 426 Upgrade Required

What does HTTP 426 mean?

The server requires the client to switch to a different protocol. The response includes an Upgrade header, for example requiring TLS or a newer HTTP version.

4xx Client error: The request has a problem the client can fix: wrong URL, missing credentials, bad data or too many requests.

426 and SEO

Rare; pages returning 426 are not indexed.

Example response

HTTP/1.1 426 Upgrade Required

How to return a 426 response

Node.js (Express)

res.status(426).json({ error: 'Upgrade Required' });

PHP

http_response_code(426);

Python (Flask)

return {'error': 'Upgrade Required'}, 426

Go (net/http)

w.WriteHeader(426)

nginx

return 426;

Related status codes

• 101 Switching Protocols — The server agrees to switch to the protocol named in the client’s Upgrade header.
• 400 Bad Request — The server cannot process the request because it is malformed.

Check which status code a URL returns with the HTTP header checker.