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.

OS: Linux Recently, firefox has been annoying me with not closing a tab when I click the X like normal. I have to right click and close it, or press ctrl w. I am unable to move tabs around, as well. I am not sure since when this next bit has been happening, but I am also unable to interact with many elements of the top bar. The only thing of the firefox ui besides the websites themselves that let me interact with them at the moment is the home button, the new tab button, bookmarked sites, and that box icon on the left corner that lets you look at previously closed tabs. My Firefox's version should around, I believe it is 140.5.0 ESR. Thank you in advance. Update: Upon a restart of firefox, it appears to be working again as normal.. However, the bit with tabs not closing when the X is clicked and not being able to move tabs around has been happening multiple previous times, and it may come back. Update again: The issue does come back after some usage. I'm using KDE plasma with Wayland. I will try what the answer asked, and come back later. Update: This seems to happen very randomly and is not reproducible for me.. It will go a few days being fine, then randomly freeze again. Has not happened under another user, at least not yet.

This problem just began today on my Win 11 laptop. Firefox is current - 139.0.4. Win 11 is current. No new software has been installed. Firefox hangs up and will not move. Task manager shows FF is consuming more than 90% of my 16GB memory. I must end the FF task to get up and running again.

im using firefox on ubuntu, version 139.0.4. when i browse the internet using firefox, every some time the toolbar and the search bar "freeze" - i am unable to click anything, from the url, to any of the buttons. it takes up to like 1/2 minutes for the search bar and the toolbar to work again. i never had this issue before, neither on ubuntu (and other linux distributions), nor on windows...

On my Windows 11 IOT Enterprise LTSC system firefox does not entirely close. After I installed my professional tax software from Drake Software LLC the following happens repeatedly: I open Firefox, look at a page, close Firefox, the screen clears and when I try to REOPEN firefox a popup says that it is still running and offers close or cancel. Neither button opens,closes or cancels Firefox. I have to reboot to make Firefox (147.02 64bit) close. This happens every time I open Firefox.

On my steam deck, from time to time, the firefox's touchscreen support seems to switch modes.

The symptoms are:

- Instead of scrolling, one-finger touch-and-drag now zooms in and out (depending on direction)
- The touchscreen no longer lets me select or close tabs, or focus or click in-page widgets
- This mode-switch is restricted to the firefox window in which it happens
  - Moving the tab to a new window results in the new window working fine
  - Other existing windows are unaffected (although they may later experience a touch mode switch  event)

I have yet to determine what triggers this switch, nor can I figure out how to undo it.

Firefox freezes when I try to sign into YouTube via Google. Becomes totally unresponsive and I have to close browser. It's the only site this happens on. I have cleared the cache and cookies, unchecked "Hardware Acceleration" and other recommendations from other posts. Please talk to me like I'm your Baby Boomer dad.

Bug Report for Mozilla Team: When you open a Gmail PDF In another window, the zoom setting has a bad response, with much delay, I inform you of this Bug So you can fix it, thank you very much.

Hi everyone,

I’ve been using Firefox as my primary browser and overall it works great, but I’ve noticed a slowdown pattern during longer sessions and wanted to compare notes with the community.

After running the browser for several hours with many tabs open, I sometimes see delayed responses when switching tabs, typing in text fields, or opening menus. Nothing crashes, but the interface feels heavier until I restart the browser. Once restarted, performance goes back to normal.

I’ve already tried reviewing extensions, disabling a few that I don’t use often, and checking memory usage in about:performance. The numbers go up as expected with more tabs, but I’m not sure how to judge what is considered normal versus problematic.

Because the issue improves after restart, I’m wondering whether this is typical resource buildup, session handling, or something specific I should be tuning.

How do experienced users usually approach diagnosing gradual slowdowns like this? Are there particular indicators in the built-in tools that suggest a real problem rather than expected behavior?

While reading more about how browsers manage memory over time, I found this general explanation helpful for understanding the bigger picture:

When I launch Firefox in Troubleshoot Mode and try to open the Settings page (about:preferences) right away, Firefox becomes unresponsive. This issue does not occur when Troubleshoot Mode is off.

I'm using Firefox 140.0.4 on macOS Sequoia 15.5.

Firefox continues to freeze up even after many FF updates. I am running Ubuntu 22.04LTS. Firefox freezes for no apparent reason. I am lucky if I can just close the browser. But often times I must do a hard shutdown of my laptop. Since the problem first appeared about six (?) months ago there have been a number of Firefox updates, but this problem continues. When will it be fixed finally?

Since a while, I think it is since I created an extra testprofile with "firefox-esr -P", but I've set my main profile as default again

When opening a link in another program than firefox I get always: a popup "Close Firefox" "Firefox is already running, but is not responding. To use Firefox, you must first close the existing Firefox process, restart your device, or use a different profile."

I do have both firefox and firefox esr, I usually use regular firefox the second came with the debian 13 repository.

I keep the esr to test display issues for reproducibility on my personal desktop, because I manage debian 13 kiosk-style desktops with firefox-esr.

(I noticed also that the regular firefox profiles can not be opened in firefox esr, so I use an extra profile for esr)

I have recently begun to have hard 'hangs' while attempting to view a video on a site I'm already connected to. I've tried to overcome these hangs, but they continue to happen even after firefox has been in use for a short time. I have to restart my computer, since the hang is locking up all control input.

I have removed many gb of apps to try and address this issue today but can't stop Firefox from using an insane amount of memory. What's up? I've been using Firefox for years and have never had this issue until today. I'd like to keep using your browser but I can't if my computer keeps shutting down.