After bug 1120501 lands the Cache Add() and AddAll() methods will immediately reject when an error occurs without aborting in-progress Fetch requests. This is mainly because the current FetchRequest() interface does provide a way to abort. There is ongoing work to expose a public way to abort Fetch requests: https://github.com/whatwg/fetch/issues/27 I think we should look at fixing this later once that spec question is resolved. If its a major problem, though, we can always implement a new internal interface for fetch that allows aborting.