Firefox Community Forum

I have 5 windows open in Firefox, yet only 1 of them is visible/accessible on the Windows Taskbar.

I know there are 5 windows open as Troubleshooting Information reports "Multiprocess Windows: 5/5"

Sometimes when I launch Firefox, the other 4 windows will be visible, and this current one will disappear. If I go to Recently Closed Windows and open that window, it will appear, but the other 4 will be hidden again.

Other times, I will launch Firefox and one window will be invisible, and it won't appear unless I close all the other windows, then it will suddenly appear out of nowhere.

I've disabled extensions, changed settings, and reinstalled multiple times, but Firefox won't quit stuttering constantly. Other browsers work fine on my computer, and Firefox doesn't seem to be using much memory.

Hello Firefox Support,

I am experiencing a consistent and disruptive performance issue that occurs immediately after certain complex web pages (particularly those with heavy scripting or dynamic content) have fully loaded.

The symptom is a temporary but complete freeze of the Firefox window, often lasting between 5 to 10 seconds, during which time the browser is completely unresponsive. This freeze is accompanied by a significant spike in CPU usage (often reaching 90-100%, according to Task Manager/Activity Monitor).

Details:

Trigger: The freeze reliably occurs right after the page status changes from "Loading" to "Done." I suspect it is related to post-load scripting execution or rendering finalization.

Impact: Any ongoing user interaction is halted until the spike subsides.

Tested Scenarios: I have replicated this on multiple sites, including heavy news aggregators, social media feeds, and complex web applications.

Troubleshooting: This issue persists even after:

Clearing cache and cookies.

Running Firefox in Safe Mode (disabling all extensions).

Creating a new, clean Firefox profile.

This severely degrades the browsing experience, especially when quickly navigating between tabs or starting a session.

Could you please investigate potential issues within the core rendering engine or script execution scheduler that might be causing these severe post-load processing bottlenecks?

Thank you.

Whenever I wake my mac from sleep, Firefox is unresponsive. I believe the app is not dead, just not repainting the window. Sometimes if I 'hide' Firefox window behind some other app window, then bring it back to top, it'll re-paint.

For a while I fixed the issue by disabling GPU usage in firefox. But now, even that isn't helping. Then for a while, removing and reconnecting the USB-C connection to my external monitor would fix it, but now that doesn't help.

Have to quit firefox completely and relaunch. Then the app is working again.

Using Firefox 146.0.1 (64-bit) on Mac (2.4 GHz 8-Core Intel Core i9, AMD Radeon Pro 5500M 4 GB, Intel UHD Graphics 630 1536 MB, 16 GB 2667 MHz DDR4, macOS 15.7.3)

I've used Firefox for years, but recently Firefox is unusable on Mac OS 15.7.2 because it's hogging all the RAM over time. I get a spinning beachball on my MacBook Pro. I look at the RAM being used and it's even over what I have in the computer. I have and always keep Firefox updated to the latest version.