Firefox Community Forum

Hi everyone,

I run a construction estimating construction estimating website where we share project-based cost estimates and detailed breakdown for contractors, architects

I’ve noticed a weird issue in Firefox lately.

Some of the heavier pages (especially ones with large tables, detailed breakdowns, and embedded content) start getting really slow or sometimes even become unresponsive in Firefox. The same pages load completely fine and smooth in Chrome, so I’m trying to understand what Firefox might be struggling with specifically.

I already tried the basic stuff like clearing cache, testing in private mode, and disabling extensions, but the issue still keeps coming back.

It seems more noticeable on pages with a lot of structured data and embedded elements, so I’m wondering if it could be a rendering, memory, or layout issue on Firefox’s side.

Has anyone dealt with similar performance issues on Firefox with data-heavy or content-heavy web pages?

What should I look into next — layout structure, CSS rendering, JS execution, or something Firefox-specific I might be missing?

Any guidance or debugging tips would be really appreciated.

I have been using Firefox forever. It has been running very slow and bugging out especially with you tube on close. I've been working on this for a couple of weeks and am about to give up. My self built system is about 10 months old. Am using a completely debloated MS 11 pro 25h2. Did not ask for AI from Firefox and have disabled AI in Firefox and copilot is long gone. I have tried everything. Am about to quit firefox. Have refreshed firefox and prevented firefox from running in MS win 11 pro "efficiency mode". I usually have to exit firefox with task manager - there are usually 17 instances of firefox running. Mozilla has become Microsoft.

The system: Gigabyte B650 mobo, 32 gig of DDR5 6000, AMD 7700X processor and an Asrock 9060 graphics card with 16 gig DDR6 Vram. All other apps are running just fine. So I don't think a lack of compute is the problem.

Help please! Thanks in advance!

When i start fire fox it immediately opens 10 additional versions in the background which I can see in task manager and they take up a lot off memory. If i end task them they immediately come back. This only started recently. I noticed it because now when i open say a youtube video it shows it as number 4. This never happened before unless I had the same video open more than once.

If I can not stop this I will have to uninstall.

Been using Firefox for over a decade. But lately is has become so slow now. Often freezes up if more than two tabs are open or a website is in any way very complex. What settings and issues should I check? What has changed? I can run the same sites on Brave and Edge browsers with no issues or not nearly as slow and bogged down.

Windows 10 Open Firefox (151.0.2) Google "does alton towers still run in the rain"

My CPU then goes to 100% continuously. Why, CPU occupancy has only gone up in the last few weeks. This happens in a lot of searches.

Hi whenever I use my Google account to sign into websites (Google, ebay, YouTube, & anyother sites,) Firefox will become unresponsive, the window containing the tab i was using becomes unresponsive, sort of. - I can't click any open Firefox Tabs, - the red 'Close' radio button is greyed-out, so I can't close any tabs or the window - right-click is unresponsive, so i can't close tabs that way, but Command-W closes the tabs normally, but the others are still unresponsive.

- i can open a new Firefox window (with &/or without Tabs,) which works normally.

- & unrelated, but earlier, Firefox was running really slowly, Youtube videos were slowed down, but audio was normal, and scrolling was slow.

Hi, I’ve been experiencing slow startup times in Firefox, especially when I have my Time calculator web app open. The browser takes longer to load and sometimes becomes unresponsive.

I’ve tried disabling extensions and changing my home page, but the issue persists. Are there any specific settings or troubleshooting steps in Firefox that can help improve performance when using online calculators like this?

Any guidance or tips would be greatly appreciated. Thanks!

How do I roll back an update that is not working on my system? I am very displeased with Firefox overall. You are a memory hog and no settings that I try help. Now, when I open a new tab Firefox freezes and I often have to close and restart, sometimes more than once. You are pushing me away from your product. I am now looking for a browser that is user friendly and compatible with my older computer (windows 10 is the most upgraded OS I can use). I hope to hear from you with a resolution soon.

I'm using v151.0 on Windows 10. The title bar disappears at random intervals and I have to close the application using Alt F4 and relaunch to restore it. I think the menu might disappear too. Otherwise I could close use File -> Exit.

Firefox dropdowns, menus and popup menus do not appear after resume from suspend on Ubuntu 22 or 24 This has been happening for only the last few weeks. Even dropdowns on web pages do not appear. I can click the dropdown and cursor down then hit ENTER to change a dropdown's value but I cannot see anything while I'm doing it. On the menus, I can use hotkeys if I remember them but the menus themselves do not appear. Right-clicking to get a context menu also does nothing but it behaves like it did. If I right click something, nothing changes on screen but if I then click another link or button, the first click is swallowed to dismiss the non-existent popup.

Other apps on the system work fine including Chromium browser.

This only occurs if I start Firefox then suspend the machine and then resume from suspend. After resume, the menus, dropdowns and popups no longer appear.

I am running Ubuntu 24.04.4 LTS on a Dell Optiplex 3050, Core i3-7100x4 , 16 GB ram, Intel HD graphics 630 (KBL GT2), Gnome 46, Wayland windowing system.

I tried Firefox safe mode, clearing the caches, etc. Nothing worked.

I am on a new PC with Windows 11, using 4 monitors. I keep trying to figure out what is making my mouse and sometimes the keyboard behave sluggish (freezes for a moment). I have takes all suggestions that AI has suggested but it is still happening. Do you have any thing for me to try? It appears to be only when Firefox is running.

• • Background:**

I'm a senior software engineer running Firefox Developer Edition on a Linux machine with 8GB RAM. I have Fission architecture (site isolation) enabled, which I understand is now the default since Firefox 95+.

• • The problem:**

When I open 20 or more tabs across different domains, Firefox's memory consumption scales dramatically — often reaching 4–6GB of RAM for what should be lightweight browsing sessions. This is significantly higher than what I observed before Fission was enabled.

• • What I've already tried:**

- Disabled hardware acceleration → no significant improvement - Set browser.tabs.unloadOnLowMemory to true → partial relief

 but tabs reload constantly, disrupting workflow

- Reduced content.notify.interval → marginal improvement - Tested with all extensions disabled (safe mode) → RAM usage

 still high, confirming it's not extension-related

- Checked about:memory → large number of separate

 "Web Content" processes, one per origin as expected with Fission

• • What I'm trying to understand:**

1. Is there a way to set a maximum process count cap for Fission

  without fully disabling site isolation? I found 
  dom.ipc.processCount but changing it doesn't seem to affect 
  Fission's per-origin process spawning behavior.

2. Is browser.tabs.min-warm-process-count a relevant setting here

  and what is the safe range to modify it?

3. Does Firefox have a built-in memory pressure threshold where

  it automatically consolidates processes — similar to Chrome's 
  memory saver — and if so, which about:config keys control it?

• • Environment:**

- Firefox Developer Edition 151.0b10 - OS: Ubuntu 24.04 LTS - RAM: 8GB - Fission enabled: confirmed via about:support - Extensions: disabled for testing

Gentlemen, isn't your browser using a lot of RAM? I've been freaking out about it in recent years. That's only with 25 tabs open!! Despite the fact that the system was installed just a day ago, without any tweaks!!!

Firefoxa używam od lat ale ostatnio strasznie mnie wkur....bo kilka aktualizacji zepsuło ten program, co aktualizacja to gorzej z wyszukiwaniem i pobieraniem np. zdjęć, nie raz nie da się odświeżyć strony, nawet wyczyszczenie historii nie pozwala na nowo wczytać strony zapisanie kolejnego zdjęcia o tej samej nazwie nie pozwala wpisać np; image 1, 2, 3 itp wklejając np: image okno jest nie aktywne by wpisać 1,2, 3, itp; trzeba czekać aż Firefox się namyśli i pozwoli dokończyć wpisywanie, szlag trafia człowieka przy takim działaniu. te wasze aktualizacje gdyby rozwiązywały problemy nie byłoby tyle poprawek Np 150.01, 150.02, 150.03 myślę, że następna aktualizacja 151 będzie bez błędów i wyeliminuje obecne bo inaczej będę musiał zmienić przeglądarkę. I jeszcze jedno wyszukując zdjęcia są one zamazywane i wielokrotnie pojawia się informacja że zmieniliście mi ustawienia przeglądarki (włączony filtr) wyłączam go ale nie ma opcji zapisania ustawień i za jakiś czas sytuacja się powtarza, zróbcie coś z tym i nie decydujcie za mnie co mam włączone a co nie. Tak samo jest z motywami niektórych nie da się usunąć a zaśmiecają kompa. Jurek

Hallo,

ich habe regelmäßig das Problem, dass Firefox quasi meinen gesamten Rechner ausser gefecht setzt indem nahezu die gesamte CPU Leistung und der Arbeitsspeicher in Beschlag genommen werden. Ich surfe in der Regel mit sehr vielen Tabs. Ab ca. 100-150 Tabs benötigt Firefox bei mir zwischenzeitlich 10 GB Arbeitsspeicher und mehr und benutzt die CPU zu 80-90% sodass der Rechner teilweise kurzzeitig nicht mehr reagiert und einfriert. Besonders, wenn ich 100 Tabs und mehr auf einmal als Lesezeichen speichere (Tabs auch nur schließen, da der CPU Lüfter schon dauerhaft auf 100% läuft), friert der Rechner danach erstmal für 3-4 Minuten ein. Ich verstehe nicht, was Firefox die ganze Zeit im Hintergrund anstellt, während z.B. 250 Tabs geöffnet sind. Tabs vorzuladen macht bei der Anzahl keinen Sinn und die Wahrscheinlichkeit, dass man richtig voraussehen könnte, welchen Tab ich als nächste wieder aufrufe und dieser dann schon vorgeladen ist, ist eher gering. Gibt es Möglichkeiten z.B.: - den zur Zeit verwendeten Arbeitsspeicher sofort zu leeren, ohne einen Tab zu verlieren oder dass Firefox geschlossen wird? - dass es dann längert dauert, wenn ich einen Tab anklicke, da dieser ja nicht mehr im Cache ist, und erst wieder in den Arbeitsspeicher geladen werden muss, ist selbstverständlich und vollkommen in Ordnung. - Kann man irgendwo einstellen, wie viele Tabs z.B. im Hintergrund aktiv sein dürfen? - Kann man den zu verwendeten Arbeitsspeicher begrenzen? - und was passiert, wenn die Grenze erreicht wird? - Kann man irgendwo an den Zeiten oder ähnlichem schrauben, wonach Tabs automatisch entladen werden? Chrome friert Tabs scheinbar automatisch ein, zu mindest ist die performance dort besser.

Es bringt ja nichts, wenn alles versuche wird im RAM vorzuhalten, damit es sofort da ist, wenn der ganze Rechner damit in die Knie gezwungen wird und am Ende das gesamte System nicht mehr zu bedienen ist. Vor einigen Jahren ist Firefox bei zu vielen Tabs oft abgestürzt, dann hat sich schon gebessert.

Es fehlt mir an Einstellungen zur Anpassung, was Firefox im Hintergrund vorhalt und was Tabs machen dürfen, wenn sie nicht aktiv bedient bzw. benutzt werden. Manuelles "entladen" kommt für mich nicht in Frage, da es zu aufwändig ist, bei extremen "Multitabbing".

Ich bin seit meiner Kindeheit begeisterter Mozilla Fan (seit Gründung von Mozilla) und verteidige und empfehle Firefox wo ich nur kann. Aber dieses Performanceproblem besteht schon sehr lange, ist zwar über die letzten Jahre besser geworden, dennoch zwingt es mich schon fast, nach einer Alternative zu suchen.

Generell fehlen viele Funktionen für Extrem-Multi-Tab-Benutzer wie z.B., dass man Tabs in der Leiste markieren oder sortieren kann. Ein großer Segen wäre eine Funktion, dass Tabs, die man bereits als Lesezeichen gespeichert hat oder doppelt geöffnete Tab, direkt zu erkennen sind, ohne dass man den Tab aufruft. Aber andere Thema. Ich benutze auch keine vertikale Tableiste, nur die horizontale klassische Leiste oben am Bildschirmrand.

Ich wäre sehr Dankbar über Tips zur Lösung des Problem mit dem Arbeitsspeicher.

Grüße