HTTP status
HTTP 426 Upgrade Required
- 426 Upgrade Required
- Client error
- RFC 9110
HTTP 426 Upgrade Required is a client error response: the client must switch to a different protocol. It is defined in RFC 9110, and the request was malformed or cannot be fulfilled as sent.
What it means
Status code426
Reason phraseUpgrade Requiredadvisory only; clients must not depend on the wording
Class4xx Client error
MeaningThe client must switch to a different protocol
Defined inRFC 9110
Cacheable by defaultNoonly cacheable if the response says so explicitly
How clients behave
Indicates an errorYes
Whose faultThe request
Body expectedUsually
Safe to retry automaticallyNo
The 4xx class
Class meaningThe request was malformed or cannot be fulfilled as sent
Codes in this class29
Lowest in class400
Highest in class451
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