426
Upgrade Required
Client ErrorThe client should switch to a different protocol given in the Upgrade header.
Category: 4xx Client Errors Standard: RFC 9110
What is 426 Upgrade Required?
HTTP 426 Upgrade Required is a 4xx status code. The client should switch to a different protocol given in the Upgrade header.
Client Request
Server
Request Rejected
Common Causes
The request was malformed or invalid
The client lacks permission or valid authentication
The requested resource or route does not exist
A precondition or content requirement was not met
Ask AI Mentor about 426 Upgrade Required
Get instant help and explanation