1982717 - Firefox locks up on macOS Tahoe (version 26)

Status: RESOLVED DUPLICATE of bug 1979283

(Core :: Widget: Cocoa, defect)

Description

[Stefan Eßer]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:141.0) Gecko/20100101 Firefox/141.0

Steps to reproduce:

Just open Firefox with a large amount of tabs (restored from the previous, crashed session).

Actual results:

Firefox locks up on macOS 26 Beta 2 after a few minutes of use.
With more than 200 tabs open, it often locks up when being opened (with tabs being restored to their previous state).
Firefox has also been observed to consume memory until it is "Paused" by macOS and must be killed to make the system return to a save state.
This issue is new in macOS 26 Public Beta 2, it did not occur in Public Beta 1 or the current release version of macOS.

Expected results:

Firefox should not consume all memory and it should not get into a locked up state that requires to force close it (since it does not react to any user input, clicks, etc.)

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:bas.schouten, could you have a look please?

For more information, please visit BugBot documentation.

Comment 3

[Stefan Eßer]

I have had my macBook lock up over night again, due to memory exhaustion.
This happens even after slight use of Firefox (I've switched the default browser to Safari due to this issue).
Even if left running in the background, Firefox will lock up after some time (hours), and if not forcefully terminated will cause all processes to be put into non-recoverable "Paused" state.
As long as this issue is not resolved, Firefox has to be terminated whenever it is not actively used and cannot be used for longer sessions.

This makes Firefox impractical on macOS, and the issue exists in all macOS 26 beta versions (which now are near release candidate status, apparently).

If Firefox is meant to be an option on macOS 26, this issue should be resolved.

Comment 4

[Bas Schouten (:bas.schouten)]

Could you include a report from about:memory (save the file from there and upload onto the bug) when you are seeing the high memory use.

Comment 5

[Stefan Eßer]

Firefox locks up hard and must be killed, it does not accept any commands in that state.
I could not reproduce the issue using Firefox, today.
Repeated click on "Show memory reports --> Measure" resulted in values between about 1500 and 3500 MB (slow growth, quick reduction back, probably due to GC runs).

But last night Firefox locked up while the system was inactive. Firefox was locked-up, but the Activity Monitor showed a total process size growing by about 100 MB per second. I'll attach 3 screenshots taken about 10 to 20 seconds apart. If Firefox is not killed in this situation, the process will consume all available memory including swap and the system will lock up and will require a reboot.

Comment 6

[Stefan Eßer]

Attachment: Activity Monitor with growing Firefox process (1)

Comment 7

[Stefan Eßer]

Attachment: Activity Monitor some 10 to 20 seconds after previews image

Comment 8

[Stefan Eßer]

Attachment: Activity Monitor after another 10 to 20 seconds

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:jlink, could you have a look please?

For more information, please visit BugBot documentation.

Comment 10

[Stefan Eßer]

Another observation: The problem occurred multiple times after first activating Firefox after the system had been idle (sleeping) over night. Firefox stayed in the typical range (memory used in the range 1.5 to 3 GB) until the Firefox windows was brought into the foreground. Firefox was locked up and marked as non-responsive by macOS. It started to grow by about 100 MB per second the moment it was brought into the foreground.

It is not possible to obtain memory statistics in this state, but Firefox did occasionally lock-up during interactive use, but with much higher probability if it had been inactive for some time and if it is then brought into the foreground.

Comment 11

[Justin Ossevoort]

I'm seeing this same problem with both and intel mac and apple silicon mac after to macOS Tahoe upgrade (final, not beta 2). On both machines with both the 142 and 143 versions of firefox. Sometimes this happens almost instantaneously (one time even before tabs were restored) and other times it keeps on working for hours on end.

I've not noticed the memory growth, but both machines have large memory, so I probably force stopped Firefox before that would become noticable.

Comment 12

[Justin Ossevoort]

Update on my earlier comment: I've seen the memory increase on both machines (intel mac and apple silicon mac).

The issue linked by 08xjcec48 made me cleanup my bookmark folders. It appears I've also managed to get the infinite recursion of bookmark folders. And since that cleanup Firefox on both machines haven't crashed yes. So that's a tentative "fixed" for my problems.

Comment 13

[squio]

Same here:

• Mac OS 26
• Firefox 143.0.1 (aarch64)

One pinned tab with Mastodon uses lots of memory but seems not the (main) cause of the freezes.

Found this Reddit post containing a lot of detailed observations which may be relevant
https://www.reddit.com/r/firefox/comments/1njn8xm/firefox_hangs_consistently_when_switching_back/

Comment 14

[squio]

(In reply to squio from comment #13)

Same here:

• Mac OS 26
• Firefox 143.0.1 (aarch64)

One pinned tab with Mastodon uses lots of memory but seems not the (main) cause of the freezes.

Found this Reddit post containing a lot of detailed observations which may be relevant
https://www.reddit.com/r/firefox/comments/1njn8xm/firefox_hangs_consistently_when_switching_back/

In can confirm that switching from System Settings to Firefox with <Alt><Tab> reliably makes Firefox non responding (showing the ‘beachball of death”)

Crash report sent to Apple

Comment 15

[fz]

That's really annoying to use the current Firefox 143.0.4 on MacOS 26.0.1 Tahoa.

Sometimes it just freezes and I have to restart, because the cursor stucks at loading and can't use it for anything else.

Also another very weird behavior was the fact of Firefox keeps working normally, but it was blocking my internet connection for most of websites in any other browser until I close it.

Just wanted to use a single browser at Windows, MacOS and iOS...

Comment 16

[fz]

Tried on Firefox Beta and the same problem happened .

Put my MacBook M4 Pro on the sleeping mode with Firefox open, and after waking up in the next day, had to force shutdown on the button and start the computer again because of a black screen with the loading mouse cursor forever.... So sad, switched to Brave Browser.

Comment 18

[natraj]

Just one more observations that Firefox has challenges with authentication based on mac passkey where the website would try to open the passkey based authentication in my case it's the fingerprint but it's neither not able to open the fingerprint authentication nor able to authenticate . This observation and it's consistent with websites like outlook.com and passkey based authentication. If this is a different but than 1995973 i will log a new bug with all the details.

Comment 19

[wendellcnichols]

I have this issue as well. However I just ran firefox for a whole weekend without it failing by putting it on its own workspace in full screen mode. Being placed in and out of the background seems to have something to do with it. Here is the first few lines of the diagnostic snap of when it fails:

`Analysis of sampling firefox (pid 75227) every 1 millisecond
Process: firefox [75227]
Path: /Applications/Firefox.app/Contents/MacOS/firefox
Load Address: 0x102ea4000
Identifier: org.mozilla.firefox
Version: 143.0.4 (14325.10.3)
Code Type: ARM64
Platform: macOS
Parent Process: launchd [1]
Target Type: live task

Date/Time: 2025-10-08 09:09:18.433 -0600
Launch Time: 2025-10-08 07:21:00.841 -0600
OS Version: macOS 26.0.1 (25A362)
Report Version: 7
Analysis Tool: /usr/bin/sample

Physical footprint: 3.7G
Physical footprint (peak): 3.7G
Idle exit: untracked

Call graph:
92 Thread_23507303: MainThread
+ 92 start (in dyld) + 7184 [0x1922b1d54]
+ 92 ??? (in firefox) load address 0x102ea4000 + 0x6690 [0x102eaa690]
+ 92 ??? (in XUL) load address 0x125604000 + 0x4f886ac [0x12a58c6ac]
+ 92 ??? (in XUL) load address 0x125604000 + 0x4f880cc [0x12a58c0cc]
+ 92 ??? (in XUL) load address 0x125604000 + 0x147ec0c [0x126a82c0c]
+ 92 ??? (in XUL) load address 0x125604000 + 0x4eefa58 [0x12a4f3a58]
+ 92 ??? (in XUL) load address 0x125604000 + 0x101ef40 [0x126622f40]
+ 92 ??? (in XUL) load address 0x125604000 + 0x101dbec [0x126621bec]
+ 92 -[NSApplication run] (in AppKit) + 368 [0x196af5720]
+ 92 ??? (in XUL) load address 0x125604000 + 0x101dd0c [0x126621d0c]
+ 92 -[NSApplication(NSEventRouting) nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit) + 72 [0x19754f664]
+ 92 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] (in AppKit) + 688 [0x19754f958]
+ 92 _DPSNextEvent (in AppKit) + 588 [0x196afcedc]
+ 92 _DPSBlockUntilNextEventMatchingListInMode (in AppKit) + 236 [0x196fe625c]
+ 92 _BlockUntilNextEventMatchingListInMode (in HIToolbox) + 48 [0x19f2981f4]
+ 92 ReceiveNextEventCommon (in HIToolbox) + 488 [0x19f10e9d0]
+ 92 RunCurrentEventLoopInMode (in HIToolbox) + 316 [0x19f10b730]
+ 92 _CFRunLoopRunSpecificWithOptions (in CoreFoundation) + 532 [0x1927cc898]
+ 92 __CFRunLoopRun (in CoreFoundation) + 2356 [0x19270ea68]
+ 92 __CFRunLoopDoBlocks (in CoreFoundation) + 396 [0x19270f624]
+ 92 CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK (in CoreFoundation) + 28 [0x19270f6e4]
+ 92 ??? (in UIIntelligenceSupport) load address 0x27d686000 + 0xea6c [0x27d694a6c]
+ 92 ??? (in UIIntelligenceSupport) load address 0x27d686000 + 0x18bf0 [0x27d69ebf0]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x44dedc [0x196f2aedc]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x44ddf4 [0x196f2adf4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b7bb4 [0x196c94bb4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b41fc [0x196c911fc]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b796c [0x196c9496c]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b76f4 [0x196c946f4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4]
+ 92 ??? (in AppKit) load address 0x196add000 + 0x1b73b4 [0x196c943b4`

Comment 20

[squio]

Confirming issue is still present with

• Firefox 144.0.2 (aarch64)
• Mac OS 26.1 (25B78)
• MacBook Air w Apple M3 - 16 GB

Just upgraded my work Macbook from Mac OS 15 to Mac OS 26.1 and there the issue does NOT happen:

• Firefox 144.0.2 (aarch64)
• Mac OS 26.1 (25B78)
• MacBook Pro w Apple M1 - 16 GB

Comment 21

[Justin Ossevoort]

Make sure to check if bug 1979283 might be applicable to your situation:

Using the bookmarks manager: check if there is a infinite loop in the folders (you can keep opening underlying subfolders endlessly)

If this is the case than you have problem from that other bug and when switching between Firefox and other applications will sometimes cause Spotlight (the search engine built into macOS) to index all menu options for Firefox and it will cause Firefox to hang (100% cpu usage and memory usage quickly increasing).

Comment 22

[squio]

@Justin Ossevoort this seems to solve the issue for me!

I couldn't find an obvious circular bookmark structure but I assembled a ton of bookmarks since the early 2000s and there were many duplicates and weird structures left over from incremental upgrades, syncs across devices (iOS, Android) etc.
I decided to completely delete my "Other Bookmarks" folder contents.

No hangs so far 🤞

This could also explain why my work laptop is not affected
Thanks!(In reply to Justin Ossevoort from comment #21)

Make sure to check if bug 1979283 might be applicable to your situation:

Using the bookmarks manager: check if there is a infinite loop in the folders (you can keep opening underlying subfolders endlessly)

If this is the case than you have problem from that other bug and when switching between Firefox and other applications will sometimes cause Spotlight (the search engine built into macOS) to index all menu options for Firefox and it will cause Firefox to hang (100% cpu usage and memory usage quickly increasing).

Comment 23

[Stephen A Pohl [:spohl] (OOO until 1/26)]

Since several people have mentioned that cleaning up bookmarks has solved the issue here, I'm going to close this as duplicate of bug 1979283. If you still encounter hangs unrelated to bookmarks, please open a new bug under widget:cocoa in order to track these issues individually.