When a service worker intercepts a request and provides a response by performing a fetch, the response's `redirected` attribute should reflect whether a redirect occurred. In Firefox today, the attribute is incorrectly set to `false` in cases where the service worker provides a response that was the result of an HTTP 302 redirect. Attached, please find a Python script that creates a web server for demonstration purposes. It may be invoked with Python 2.7 as follows: python sw-redirect.py And subsequently accessed by navigating to `http://localhost:9000`. Demonstration results are printed to the developer's console. Expected: In worker: > response.type = basic > response.status = 200 > response.redirected = true In client: > response.type = basic > response.status = 200 > response.redirected = true Actual: In worker: > response.type = basic > response.status = 200 > response.redirected = true In client: > response.type = basic > response.status = 200 > response.redirected = false System information: - Firefox: 55.0a1 (2017-05-12) (64-bit) - Platform: GNU/Linux (Ubuntu 16.04)

So if I'm reading this right, the Response returned in the outer window is the one with the wrong .redirected value. So this is a bug in our code that synthesizes nsIChannel from Response in SW and then extracts Response back from nsIChannel on the main thread.

Fixed by bug 1222008.