Cache.addAll methods were storing
5xx error responses from
fetch. This behaviour had confused developers, therefore the spec has been changed to reject any responses with a non-
2xx HTTP status code where the
Response.ok property becomes
false, and raise a
TypeError. Firefox 46 and later follow the updated spec.
As a side effect, those methods will always reject
opaque responses returned as the result of
no-cors cross-origin requests, because such responses have the
0 status code instead of the actual code. This is a rare case at this moment according to the Blink team.