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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+ and have at least 2 GB RAM. For users with less than 4 GB of physical memory, there is a trade-off between the larger virtual address space and the overhead of 64-bit code. 2 GB RAM is Microsoft's minimum memory requirement for Windows 7 and 10.


  • 2014 Q3
    • [DONE] August 8 - Chrome's 64-bit announcements: Mac and Windows
  • 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 the stub installer's default in Nightly 53 (bug 797208). The 64-bit default did not ride the trains with 53. The 64-bit installer option shipped in 54.
  • 2017 Q1
  • 2017 Q2
    • [AT RISK] April 12 - Enable Flash async drawing in Aurora 54 (bug 1340934)
    • [DONE] April 18 - Firefox 53 release (with 64-bit installer option)
    • [DONE] May 2 - Google began migrating 32-bit Chrome users (with more than 4GB RAM) to 64-bit Chrome 58.
    • [DONE] May 8 - Flash release with fix for acceleration regression bug 1359886.
    • [ON TRACK] June 13 - Firefox 54 release
    • [AT RISK] June 13 - Flash 26 (York) release should fix zero-sized Flash bug 1348629.
      • [PROPOSED] Ask Softvision to test async drawing with Flash 26 release and then re-enable async drawing for 32-bit Flash.
    • [PROPOSED] June 21 - Begin Funnelcake experiment to compare 32-bit vs 64-bit for eligible Release 54 users: 120K users in de, es-ES, fr, pt-BR, and ru. (bug 1309844 and bug 1309847)
    • [PROPOSED] June - Write technical blog post about 64-bit installer default in 55.
    • [PROPOSED] June - Write consumer blog post about 64-bit migration in 56.
  • 2017 H2
    • [AT RISK] July - Re-enable Win64 tests on Try by default? (bug 1359506, blocked waiting for Windows 10 Taskcluster bug 1326419)
    • [ON TRACK] August 8 - Firefox 55 release (with 64-bit installer default)
    • [PROPOSED] August - Publish technical blog post after 55 release so the new installers are available.
    • [PROPOSED] September - Publish consumer blog post before 56 release so users can set the opt-out pref before we upgrade 32-bit users.
    • [ON TRACK] October 3 - Firefox 56 release
    • [PROPOSED] October - Migrate eligible 32-bit Firefox users to 64-bit (bug 1274659) with a 56.0.1 release.

Release Criteria



ID Priority Summary Whiteboard Keywords Assigned to
1344220 -- Enable stub installer downloads for win64 for all desktop Firefox channels
1375472 -- Reexamine install timeout as a consequence of new 64 bit Firefox install default
1310163 -- Win64 Funnelcake comparative user sentiment Heartbeat experiment Rob
1367054 P1 add support for memory in SYSTEM_CAPABILITIES field
1334803 P1 Xfinity TV video playback fails in 64-bit builds of Firefox [Xfinity cloud dvr feature related?][sb+] David Parks (dparks) [:handyman]
1294602 P2 plays in 32-bit, fails with Media Error in 64-bit
1321493 P2 NPAPI sandbox is blocking Flash RTMPS SecureSocket from using Windows certificate APIs on Win64 sb+

7 Total; 7 Open (100%); 0 Resolved (0%); 0 Verified (0%);

ID Priority Summary Whiteboard Keywords Assigned to
1311975 P2 Cannot interact with Flash Video Controls on certain site gfx, STR in comment #0 (32bit only) regression
1306698 P3 When resize content/window, image under the flash plug-in is briefly display layout, STR in comment #0 regression
1347925 P3 wmode direct flash reverts to windowed mode if browser hardware acceleration is disabled
1347575 P4 Disabling acceleration in flash breaks flash settings dialog on
1276426 P5 Flash video stops when switching between tabs hold, STR in comment #0 regression

5 Total; 5 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