I seem to be having a lot of problems with my Firefox install. One of these is that it uses a lot of memory, but I'm not sure if it's normal or not.

After a few hours of browsing it can go up to 800MB of RAM. I watch a fair amount of videos on youtube and play the occasional Flash game. In combination with the "plugin-containers" it can even reach 1.1-1.2GB of RAM.

I'm using Waterfox, a 64bit mod of Firefox 7, but even when using Firefox 4 I've had this issue. It runs on a 64bit Windows 7 PC.

I usually have 3-5 tabs open, sometimes up to 10. But once i close those, it'll still use about the same amount of memory. Installed plug-ins are only Greasemonkey and Downloadhelper.

Is this normal or not? Can I do anything about it?

  • You need to specify what extensions you are using and how many tabs you have open. – surfasb Oct 6 '11 at 16:06
  • @surfasb: added ;) – Simon Verbeke Oct 6 '11 at 16:11

It's not abnormal if your system has sufficient RAM for Firefox to be able to cache that much data. The more tabs or pages you have open, the more RAM it'll use. Each page that has to be rendered has to be processed and stored in RAM. All the images have the be decompressed, the HTML and CSS has to be parsed, and the JavaScript compiled. All this data is stored in RAM for each page that's open. The more pages that are open, the more RAM that is required to store all that information to allow switching tabs to be instantaneous. In some cases even the history of previous pages is stored to allow the Back button to switch the previous page without having to reload the page from the internet.

It'll also use RAM as a cache to avoid re-downloading images and files that you've already downloaded in order to speed up the experience.

As long as the RAM usage caused by Firefox is still leaving sufficient physical RAM available for other applications, then it's not a problem. Use the task manager to see how much physical RAM you still have available, and if it's at least 500-1000MB free, then just enjoy the benefit of having enough RAM to have a large cache that increases browsing speeds.

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  • While your answer is correct in a system-wide sense, it's not correct when applied to Firefox directly. RAM used by the file cache isn't charged to any processes. While Firefox does have its own memory cache, it maxes out at 32 MB by default. (Source) – afrazier Oct 6 '11 at 16:26
  • Maybe my answer wasn't clear. RAM in Firefox is utilized in two ways. One use is to contain the entire process contents of a web page, including the decompressed contents of all images. RAM is required simply to render the page. The second use is a file cache. The first use is what takes up the most RAM. – Chris Thompson Oct 6 '11 at 16:48

Yes it's normal and not limited to Firefox. Chrome does the same thing, except, because chrome also runs 10 or more processes depending on the tabs you have open, it doesn't appear to use quite so much. Add up all the processes, though, and you get some pretty startling numbers.

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Firefox 7 greatly improves on memory use over prior version. This is not normal anymore for most users. Exceptional users with many (>50) tabs open at a time may see something like this happen.

I'm using Waterfox, a 64bit mod of Firefox 7

I suspect the Waterfox incorrectly accounts for the new memory management improvements from standard FF7.

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  • I don't think this is the problem - the regular version, which I used up until a few days ago, did the same. – Simon Verbeke Oct 6 '11 at 16:35

Nothing to say about 64-bit, but for few hous and tabs it seems, well, terrible.

Just idea - can you try native 64-bit Palemoon 7 x64 without any plugins and compare results for usual day. Also, Flash may be main reason - there aren't 64bit player from Adobe AFAIK

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