Flame-kk, Build identifier is 20151115150212 Try to open  in b2g browser and observe logcat and "Service Workers" panel in Settings app: * Logcat: I/Gecko ( 8260): WARNING: child tried to open http IPDL channel w/o security info E/Browser ( 8260): Content JS ERROR: Registration failed with [Exception... "Illegal value" nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)" location: "native frame :: <unknown filename> :: <TOP_LEVEL> :: line 0" data: no] E/Browser ( 8260): at swRegistrationPromise< (https://fxos-performance.github.io/service-worker-simple-fetch/js/app.js:23:7) * Settings app: I see SW is listed there, but it disappears once I restart device. The same page seems to work correctly in latest the Firefox Nightly.  https://fxos-performance.github.io/service-worker-simple-fetch/
This is a known issue. You have to disable the network.disable.ipc.security pref on b2g right now.
Yep, that fixes the issue thanks! I was confused by WebIDE that was showing "true" for this pref, but didn't work for me before I run WebIDE - it turned out that when you request "higher privileges" via WebIDE - it sets this pref to "true" under the hood :)