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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
    • [AT RISK] February - Enable Flash async drawing in Aurora 53
    • [AT RISK] February - Announce ctypes deprecation
    • [AT RISK] February - Forbid ctypes in AMO's add-on validator (for Firefox 52?)
    • [ON TRACK] March 7 - Firefox 52 release
    • [PROPOSED] March - Run Funnelcake test to compare 32-bit vs 64-bit for eligible Release 52 users
    • [ON TRACK] Fix Flash sandbox bugs
    • [AT RISK] - March - Plugin-free WebRTC Hangouts should be live
  • 2017 Q2
    • [ON TRACK] April 18 - Firefox 53 release (with 64-bit default)
    • [PROPOSED] April - Announce 64-bit default for new installs for Firefox 53
    • [ON TRACK] June 13 - Firefox 54 release
    • [PROPOSED] Google to migrate 32-bit Chrome users to 64-bit?
  • 2017 H2
    • [ON TRACK] August 8 - Firefox 55 release
    • [PROPOSED] Migrate existing eligible 32-bit Firefox users to 64-bit (bug 1274659)
    • [ON TRACK] October 3 - Firefox 56 release
    • [ON TRACK] November 28 - Firefox 57 release

Release Criteria



ID Priority Summary Whiteboard Keywords Assigned to
1268470 -- crash in klsihk64.dll@0x3ad7 64bit, crash
1297247 -- Add win64 build support to libyuv Sotaro Ikeda [:sotaro]
1310163 -- Win64 Funnelcake comparative user sentiment Heartbeat experiment Rob
471090 -- [meta] Windows x64 build tracking bug meta Makoto Kato [:m_kato]
1323460 -- Hang at RtlpLookupDynamicFunctionEntry when stackwalking in Win64 builds hang, reproducible Hannes Verschore [:h4writer]
1302078 -- Rust panic handling broken on Win64?
1309847 -- Optimizely Win64 A/B testing
1321493 -- NPAPI sandbox is blocking Flash SecureSocket from using Windows certificate APIs on Win64 sb+
1308506 P2 Investigate discrepancy between 64bit and 32bit on octane
1276558 P3 Crash in `anonymous namespace''::TypeAnalyzer::insertConversions crash

10 Total; 10 Open (100%); 0 Resolved (0%); 0 Verified (0%);

ID Priority Summary Whiteboard Keywords Assigned to
1311524 -- Buttons are inaccessible in a new window with Flash (poker's website) gfx regression
1314935 -- Flash game would not respond with key / mouse [DUPEME] regression
1311975 -- Cannot interact with Flash Video Controls on certain site gfx regression
1321866 -- Wrong size of Flash plugin when open many tabs
1312369 -- dom.ipc.plugins.asyncdrawing.enabled changes mouse wheel behavior sitecompat regression Jim Mathies [:jimm]
1325118 -- Flash crashes in Windows debug builds
1312688 -- Cannot type some special characters in input text fields in Flash/Flex content with various keyboards (Polish, French) input regression, testcase
1311374 -- Video fails to update after exiting full screen and scrolling the video in and out of view gfx, layout regression
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
1311985 -- massive performance decrease with certain Korgregate games when using async drawing mode repo? regression
1323403 -- Flash Player on doesn't work when Flash is windowless regression Makoto Kato [:m_kato]
1312648 -- Website does not work with Firefox 49.0.2 regression
1306698 -- When resize content/window, image under the flash plug-in is briefly display layout leave-open, regression David Parks (dparks) [:handyman]
1328040 -- Flash plugin context menu (even if closed) prevents the 1st click on UI and fires 'click' on html document regression
1314467 -- Huge performance regression when Flash object is opened in many tabs [parity-chrome] [parity-edge][qawanted , help gecko profile] perf, qawanted, regression
1290528 P3 WINDOWPOS y coordinate in Nightly 50.0 is off by one from Release 47.0
1316438 P3 Flash plugin doesn't render most of display on Nightly with async painting enabled [gfx-noted], regresion from bug 1312242
1276426 P5 Flash video stops when switching between tabs hold regression

19 Total; 19 Open (100%); 0 Resolved (0%); 0 Verified (0%);

ID Priority Summary Whiteboard Keywords Assigned to
1329328 -- 64-bit Firefox on Win10 - Flash Downloads result in OS Permission errors sbwn1
1284897 P3 64 bit Flash Player has storage permissions issues sbwn1 64bit David Parks (dparks) [:handyman]

2 Total; 2 Open (100%); 0 Resolved (0%); 0 Verified (0%);

ID Priority Summary Whiteboard Keywords Assigned to

0 Total; 0 Open (0%); 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