426
Upgrade Required
4xx Client error
Class
RFC 9110 §15.5.22
Defined in
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 RequiredRelated 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.
All HTTP status codesSearch the full list of status codes from 100 to 599 with their meanings and SEO impact.
Open the full list Frequently asked questions
What does status code 426 mean?
426 Upgrade Required: The server requires the client to switch to a different protocol.
Does 426 affect SEO?
Rare; pages returning 426 are not indexed.