Response Codes

It is possible for your client and server to become out of sync due to caching and long-polling. In this case your server should respond with a specific status code to let the frontend know why a request might not have succeeded.

The recommended status code is 424.

However, there are several status codes that also make sense.

• 412 - Precondition Failed
• 417 - Expectation Failed
• 422 - Unprocessable Entity
• 426 - Upgrade Required

They all make enough sense that you should just pick one and stay consistent with it.

If you want to look through other possible codes, check out https://http.cat or https://httpstatuses.com/