Open Bug 1563966 Opened 4 months ago Updated 4 days ago

Firefox unable to render tab: Shows spinning drain on white background with high CPU and memory allocation


(Firefox :: Untriaged, defect)

67 Branch
Not set





(Reporter: trussent, Unassigned)


User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0

Steps to reproduce:

Used firefox. I have many tabs in my window. I selected a not yet loaded tab to view it with a mouse click on the tab bar on the top. In all cases I was trying to load a tab from a website that I have been to many times both in previous sessions of firefox and after restarting firefox.

Actual results:

firefox is unable to render the tabs contents and shows only the spinning drain on the tab. This can happen after selecting one tab or twenty, but it has happened to me ten times or so this morning.

Also memory is steadily consumed and the cpu is pegged. The firefox process must be killed with task manager.

Expected results:

The tab, which has the address prepopulated from the option to restart with previous tabs, should have loaded and rendered in a short time.

When this problem arises, it only cripples one window, if there were others open. Other windows are unaffected, until this problem occurs in them separately.

Also upon requesting an exit from the file menu all the windows close, and only one of the many firefox processes remains in memory consuming cpu and growing memory allocation.

Summary: Version 67.0.4 64 bit. After an update yesterday, firefox becomes unable to render a tab. It only shows the spinning drain on a white background. Also, the firefox process pegs the CpU and begins to grow its memory allocated as shown in task manager. → Firefox unable to render tab: Shows spinning drain on white background with high CPU and memory allocation


I cannot reproduce this issue on Firefox 68 (2019-07-05) or Firefox Nightly 70.0a1 (2019-07-10)

Please test if the issue occurs in safe mode. Here is a link that can help you with that:

If the issue is still occuring, test it with a new profile, you can find the steps to do that below:

Thank you for reporting!

Flags: needinfo?(trussent)

Thank you for checking in on this.

I have not been able to reproduce this error in safe mode although I have tried. Further, I have been using four firefox windows to hold my current 246 tabs for the past four days and this problem has not arisen outside of safe mode either, except for one case in one window, which had started with about 275 tabs, but had been reduced to about 145 before the window died.

Today, I put all of these tabs, 246, back into one window and have not had the problem arise yet, but will leave it in this state to see if it shows the problem in the future.

Because I closed about thirty tabs this weekend after getting this problem (prior to splinting the tabs up among windows), I am going to speculate that at 256 tabs in a window the rendering engine loses track of what it is doing and blows out a memory leak.

Flags: needinfo?(trussent)

Ok, I combined all of my tabs into one window and kept one other window with only this tab. Operating firefox this way did not have the problem arise. Until yesterday when I received another update. Now one of the tabs in the window with many tabs has seized up in this way three times this evening and once yesterday. I have now restarted my session, with both windows, in safe mode, and will browse normally until it either seizes up or microsoft forces a reboot on Tuesday. Thank you for your patience.

Upon the switch to safe mode firefox did not have a tab rendering lock up, but after a few hours the memory consumed exceeded 15gb by all the firefox processes. The largest process was allocated over 7gb. I exited firefox and restarted not in safe mode. Hope this helps.

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