- Install fresh version of Firefox 47.0.dmg on high-end Macbook Pro
 - Before launch, remove all old profiles
 - Do not install any addons
 - Enable Tracking Protection
 - Use browser normally (Logging into email, pinning a couple tabs, surfing on max 10 additional tabs)
 - Firefox Quantum is so fresh and fast, loving it!
 - Bu then: Between 10 minutes and 4 hours later, all Apps grinds to a halt.
 - Entire Mac becomes nearly unusable while I crawl through activity monitor to force quit
 - Sometimes if I cannot Force Quit Firefox in time, the system recovers
 - Otherwise, force close Firefox and Apps comes back to life
 - Checking "about:crashes" often has no results :( This means I cannot send a bug report with the crash.
 - Go back to Chrome and whimper b/c it feels so slow now, but does not destroy my computer at irregular intervals

 - Resetting Firefox Profiles
 - Deleting all profiles
 - Tried FireFox Developer Edition, had the same problem
 - Tried beta, had the same problem
 - Now trying Nightly. Will report back on results.

First of all, thanks so much for any support and all the hard work on Firefox! Hope this report helps / finds like-minded souls who want to use Firefox but see it grinding their system to a halt after a bit of usage. Repro: - Install fresh version of Firefox 47.0.dmg on high-end Macbook Pro - Before launch, remove all old profiles - Do not install any addons - Enable Tracking Protection - Use browser normally (Logging into email, pinning a couple tabs, surfing on max 10 additional tabs) - Firefox Quantum is so fresh and fast, loving it! - Bu then: Between 10 minutes and 4 hours later, all Apps grinds to a halt. - Entire Mac becomes nearly unusable while I crawl through activity monitor to force quit - Sometimes if I cannot Force Quit Firefox in time, the system recovers - Otherwise, force close Firefox and Apps comes back to life - Checking "about:crashes" often has no results :( This means I cannot send a bug report with the crash. - Go back to Chrome and whimper b/c it feels so slow now, but does not destroy my computer at irregular intervals Solutions Tried: - Resetting Firefox Profiles - Deleting all profiles - Tried FireFox Developer Edition, had the same problem - Tried beta, had the same problem - Now trying Nightly. Will report back on results.