What does HTTP status code 426 mean?
The 426 Upgrade Required status code indicates that the server refuses to execute the request unless the client upgrades to a newer protocol (like HTTP/2 or TLS 1.3).
When to use it in APIs
Used to force old API clients or mobile apps to update their connection libraries to support secure protocols.
How it compares to other codes
- 101 Switching Protocols: An agreement by the server to switch. 426 is a requirement that the client upgrade before proceed.
