I’m pleased to announce that we now recommend normal Nightly builds for testing our implementation of Service Workers. We will not be posting any more custom builds here.
Now that bug 1110814 has landed in mozilla-central, Nightly has roughly the same functionality as the last sw-build. Just enable these preferences in about:config:
Please note that on Firefox OS you must enable an additional preference as well. See bug 1125961 for details.
In addition, we’ve decided to move forward with enabling the Service Worker and Cache API preferences by default in non-releases builds. We expect the Cache preference to be enabled in the tree today. The Service Worker preference should be enabled within the next week once bug 931249 is complete.
When Nightly merges to Aurora (Developer Edition), these preferences will also be enabled by default there. They will not, however, ride the trains to Beta or Release yet. We feel we need more time stabilizing the implementation before that can occur.
So, unfortunately, I cannot tell you exactly which Firefox Release will ship with Service Workers yet. It will definitely not be Firefox 39. Its possible Service Workers will ship in Firefox 40, but its more likely to finally be enabled in Firefox 41.
Developer Edition 39, however, will have Cache enabled and will likely also have Service Workers enabled.
Finally, while the code is stabilizing you may see Service Worker registrations and Cache data be deleted when you update the browser. If we find that the data format on disk needs to change we will simply be reseting the relevant storage area in your profile. Once the decision to ship is made any future changes will then properly migrate data without any loss. Again, this only effects Service Worker registrations and data stored in Cache.
As always we appreciate your help testing, reporting bugs, and implementing code.