Firefox Community Forum

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.

After update tahoe 26.1 update on mac firefox keeps stalling are they fixing this before i switch? I have a lot of tabs and things here but if you keep freezing I am going to switch. Are they fixing this? I already did all the things you suggest online. It freezes, and I can't keep this up?

I've been using Fire Fox for decades, but lately it is so slow, I thought there was something wrong with my Windows 7 ultimate. I've done full Windows reboot, to no avail. Then I see the internet t hat FireFox is starting to implement AI. I thought that may be the issue, but after looking into it, looks like that isn't an option with my old Win 7 OS. So if that isn't the problem, how can I find out what is bogging Fire Fox down? I keep a watch on my CPU usage, and the usage is going nearly to 100%, when it used to barely go over 10%. When I check the actual CPU usage, it shows as many as 15 or more items tied to Fire Fox.

Is this all a result of continued use of Win 7? I'm planning to move to Linux, but that will take me some serious time and effort. Gerald

i run Firefox on Win11. When i go to a website, and open several tabs, e.g., 10 or more, firefox just sits there and no longer works on that site. Basically Firefox is becoming quite worthless as a browser for me. The reason i use it are the extensions. This is something that has happened within the last 6 to 9months or so. What is going on. Is there now some limitation of how many tabs you can open? The site with this problem is: https://www.bellazon.com/main

Anyone got any ideas as to what is going on here?