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Make 64-bit Firefox the default version for new and existing eligible users to reduce our OOM crash rate, increase performance, and improve security (ASLR).

Users are eligible for a 64-bit default if they are running 64-bit Windows 7+. 32-bit Firefox running on 64-bit Windows can access about 3,800 MiB of virtual address space (4 GiB minus overhead from physical memory reserved for the OS and BIOS). For users with less than 4 GiB of physical memory, there is a trade-off between the larger virtual address space and the overhead of 64-bit code. We have decided to remove any minimum memory requirement for 64-bit Firefox because we don't want to withhold the security benefits of ASLR. Also, 2 GiB RAM is Microsoft's minimum memory requirement for Windows 7 through 10.


  • 2015 Q2
  • 2015 Q4
  • 2016 Q3
    • [DONE] July 20 - Announced NPAPI to be removed in Firefox 52: Reducing Adobe Flash Usage in Firefox
    • [DONE] August 29 - Web team will start redesigning download page redesign for 64-bit
    • [DONE] September 23 - Web team will start A/B test of new download page
  • 2016 Q4
    • [DONE] October 7 - Web team will complete A/B test of new download page
    • [DONE] October - Drop support for non-Flash NPAPI plugins in Nightly 52 (bug 1269807)
    • [DONE] October - Create dashboards for 64-bit rollout criteria
    • [DONE] November 24 - Make 64-bit Firefox the default in the stub installer for all eligible users in Nightly 53 (bug 797208)
  • 2017 Q1
  • 2017 Q2
    • [ON TRACK] April 18 - Firefox 53 release
    • [ON TRACK] June 13 - Firefox 54 release
    • [PROPOSED] June - Run Funnelcake test to compare 32-bit vs 64-bit for eligible Release 53 users
    • [PROPOSED] Google might upgrade 32-bit Chrome users to 64-bit mid-2017?
  • 2017 H2
    • [ON TRACK] August 8 - Firefox 55 release (with 64-bit default)
    • [PROPOSED] August - TBD: Announce 64-bit default for new installs of Firefox 55? Or wait until we upgrade 32-bit users?
    • [ON TRACK] October 3 - Firefox 56 release
    • [PROPOSED] Upgrade existing eligible 32-bit Firefox users to 64-bit (bug 1274659)

Release Criteria



ID Priority Summary Whiteboard Keywords Assigned to
1333486 -- Crash in @0x0 | idmcchandler7_64.dll@0x238bf crash Jorge Villalobos [:jorgev]
1338170 -- Crash in @0x0 | ffi_call [Internet Download Manager] crash
1340934 -- Re-enable Flash async drawing Jim Mathies [:jimm]
1310163 -- Win64 Funnelcake comparative user sentiment Heartbeat experiment Rob
1329328 -- 64-bit Firefox on Win10 - Flash Downloads result in OS Permission errors sbwn1 David Parks (dparks) [:handyman]
1336517 -- Issues with perf
1302078 -- Rust panic handling broken on Win64?
1309847 -- Optimizely Win64 A/B testing
1317995 -- Firefox 50 64-bit Stable channel is unable to play Farmville 2 Facebook Flash game. [platform-rel-Zynga] 64bit, flashplayer, regression, site-compat
1342347 P1 Revert stub installer default from 64-bit to 32-bit on Aurora 54 Matt Howell [:mhowell]
1309844 P2 Funnelcake build request to support Win64 A/B testing
1339870 P2 Win 64 stub installer on aurora defaults to installing en-us Matt Howell [:mhowell]
1276558 P3 Crash in `anonymous namespace''::TypeAnalyzer::insertConversions crash

13 Total; 13 Open (100%); 0 Resolved (0%); 0 Verified (0%);

ID Priority Summary Whiteboard Keywords Assigned to
1323403 -- Flash Player on doesn't work when Flash is windowless STR in comment #0 regression Makoto Kato [:m_kato]
1312369 -- dom.ipc.plugins.asyncdrawing.enabled changes mouse wheel behavior sitecompat regression Jim Mathies [:jimm]
1328040 -- Flash plugin context menu (even if closed) prevents the 1st click on UI and fires 'click' on html document regression
1312688 -- Cannot type some special characters in input text fields in Flash/Flex content with various keyboards (Polish, French) input regression, testcase
1306698 -- When resize content/window, image under the flash plug-in is briefly display layout, STR in comment #0 leave-open, regression David Parks (dparks) [:handyman]
1339873 -- Comedy Central Flash videos playback is choppy
1314491 -- Kongregate's Flash game doesn't load with Flash protected mode disabled and plugin asyncdrawing enabled hold regression
1311740 -- Since latest update of flash update, Firefox lags and freezes repo? regression
1342092 -- Wheel input issues with Farmville 2 regression
1321866 -- Wrong size of Flash plugin when open many tabs STR in comment #0 (intermittent)
1311985 -- massive performance decrease with certain Korgregate games when using async drawing mode repo? regression
1323750 -- Flash Stage3D fails on in 64-bit Firefox regression
1312648 -- Website does not work with Firefox 49.0.2 regression
1335733 -- flash doesn't respond to mouse when window is maximized (Nightly regression) regression
1314467 -- Huge performance regression when Flash object is opened in many tabs [parity-chrome] [parity-edge][qawanted , help gecko profile] perf, qawanted, regression
1311374 -- Video fails to update after exiting full screen and scrolling the video in and out of view gfx, layout, STR in comment #0 regression
1339875 -- Video on plays back poorly regression
1314935 -- Flash game would not respond with key / mouse [DUPEME], STR in comment #0 regression
1311975 -- Cannot interact with Flash Video Controls on certain site gfx, STR in comment #0 (32bit only) regression
1290528 P3 WINDOWPOS y coordinate in Nightly 50.0 is off by one from Release 47.0
1276426 P5 Flash video stops when switching between tabs hold, STR in comment #0 regression

21 Total; 21 Open (100%); 0 Resolved (0%); 0 Verified (0%);


Role Contact
Product Management Romain Testard
Engineering David Parks (Flash sandbox), Matt Howell and Robert Strong (installer), Stéphanie Ouillon (Flash sandbox review)
QA Ryan VanderMeulen
UX Michael Verdi (Firefox), Jon Petto (
Release Management Sylvestre Ledru
Release Engineering Chris AtLee
Firefox Program Management Chris Peterson Program Management Jennifer Bersch
Add-ons Jorge Villalobos