What does HTTP 428 mean?
The server requires the request to be conditional.
Common causes and when you see it
Prevents lost updates by requiring If-Match.
How to fix or handle it
Send an If-Match header with the latest ETag.
Test it yourself
Send a request with the online API tester, inspect the response with the HTTP header checker, or host an endpoint that returns 428 with the mock API generator to see how your app reacts.
HTTP 428 questions
The server requires the request to be conditional.
Prevents lost updates by requiring If-Match.
Send an If-Match header with the latest ETag.