I-Firefox Community Forum

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.

• • 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

This new issue is puzzling:

Normally, on MacOS, when you minimize an app that's currently running and occupying the desktop, say by clicking the orange button at top left or by clicking another app, its menu would disappear from the top toolbar and other apps could then be invoked. Clicking that app icon again would restore it to the screen and its menu would again be on the top toolbar.

But Firefox has stopped allowing that behavior: Now, when I try to minimize Firefox, while its screen minimizes (revealing the desktop underneath), its menu remains on the top toolbar. It is as if Firefox refuses to let go of the controls. So, while you can see the other icons on the desktop - say file folders - they are unresponsive to clicks and do not open when you click them, as if Firefox is not letting you access File Manager.

Furthermore, you can still access these desktop file folders, but only by opening the finder using the bottom toolbar menu, not by clicking the file icons directly.

For what it's worth, all menus are still responsive (bottom toolbar, top toolbar, apple menu), just nothing that's on the desktop responds when Firefox is still running, despite being minimized.

After installing Firefox 150, clicking on a window for a different application does not make that application active. Firefox is not letting me leave! I can switch by going to the sidebar and choosing a different application. None of the other applications exhibit this behavior. MacOS 26.3.1

Since updating to 152.0.4 on 30 June firefox has frozen multi times a day, nothing is responsive. I've had to force close and restart. I performed suggest hang fixes, refresh, changes places names, turned off accelerations. None of that resolved the issue. I did not have this issue prior to 152.0.4. No crashes, just hangs forcing restarts - but each one forces me to re-enter all my user information for the various sites I'm using. I've see some references of similar issues with others having upgrading to 152.0.4, but there don't appear to be any clear fixes. Is this issue being evaluated?

After latest update Firefox Developer Edition 151.0 Beta 4 I noticed much slower website loading while using few containers at the same time and overall more lag. Before the update everything was great and smooth I hope it's gonna get fixed soon.

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.

I started noticing my browser was running rough, and I tracked it down to Youtube, but only when I have a video in fullscreen. It doesn't appear to be affected by the codec, av0/avc/vp09 all suffer from it.

Incognito mode (no extensions) is still affected by it, but a separate profile + troubleshoot mode are not. My RTX 5080 is showing about 2% usage when playing a video, 0% at idle.

How do I nail down what's causing this?

Two questions; First is why does the Taskbar show "Firefox (2)" (see first image) Second: When trying to troubleshoot, I open Task Manager, and with just one tab open, I see Firefox (13); confirmed when the line is expanded. What is going on here and is it impacting Firefox performance; see 2d and 3d images? (Phone camera photos as PrintScreen is disabled for Task Manager which doesn't seem smart)

after working in firefox for a while and using a number of windows and the I close firefox with multiple windows open in my session. if i open it again and keep doing this for a while and then have closed firefox, eventually I can no longer open a firefox window and get a message the I have too many windows opn and can't open more till i close the open windows. i hover over the firefox app and all the previously closed windows are stacked up. why didn;t they close when i exited my firefox sessions. why are they still there and clogging up the system?

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

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.

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 recently upgraded from Ubuntu 24.04 to 26.04, using Mate Desktop and Compiz compositor. I am using Firefox from the Mozilla Team PPA, currently 150.0.1. I am running custom kernel built from upstream source, currently 6.18.25. Hardware is a home brew CoffeeLake machine, i7-9700k, 64G of RAM, 2TB WD Black SSD and many TB's of spinning rust, graphics is Intel ARC B50 Pro, ASUS XONAR SE 5.1 Channel 192kHz/24-bit Hi-Res 116dB SNR PCIe Gaming Sound Card. Prior to upgrading Firefox was not 100% occasionally tabs would wedge, now if I get two hours I'm doing good, I've tried disabling extensions and plugins no help. Tried with and without hardware decoding, worse without but bad no matter. Any suggestions how to get stability back?

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.

When I launch Firefox, it uses well under 1GB in memory, but then it starts to increase that amount quickly in just a few minutes and gets up to 50+GB, causing error messages to pop up repeatedly until it uses all resources and locks up my computer. I have updated my MAC OS and the Firefox app, uninstalled the Firefox App and still have the same problem.

Please help