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I've an old PC (Dell Optiplex GX50) with an Intel Pentium III CPU @768Mhz and 256MB of RAM, with Windows XP. When I booted it yesterday, Firefox 3 was installed (and nothing else). Openning 2 tabs (Youtube main page, Google), it was consumming around 60-70MB of RAM. Now I installed Firefox 27, and it is consumming 140MB of RAM with the same 2 pages loaded. With Firefox 3, I was able to load several tabs, around 15-20 and it started to slow down. Now a few tabs and it consumes all the RAM.

Why, from Firefox 3 to Firefox 27, RAM consumption has doubled without using any special functionnality and only loading 2 pages ? I know there were many new functionnalities added, but here I'm not using anything special. Mozilla also stated they were trying their best to limit RAM consumption. (as we all know since Firefox 4 it has increased much).

So, how to limit RAM consumption on this old PC ? Is there a way to disable unused functionnality, and which are those ?

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Firefox only using 27MB thats actually pretty good my installion uses about 2.7GB :-) Simple explaination....Firefox 3 has less features then the current version of Firefox – Ramhound Mar 5 '14 at 19:48

Your answer is in your question:

there were many new functionnalities added

Even if you don't use new features, the browser has to have them prepared at any time. It's how computer programs work. Also, no visible change in functionality doesn't mean no change in underlying code, and thus - memory consumption can change too.

Trying to keep memory usage as low as possible doesn't necessarily mean keeping it as low as in previous version. It's a very rare case for programs to use less RAM than previous versions. In this case we're talking about a difference of 26 versions (FF 3.5, 3.6, 4.0-27.0), or 6 years between release dates. That's a lot of versions.

According to Moore's law computational power of computers has increased about 8 times since the release of Firefox 3. Don't expect modern versions to be designed for such old hardware.

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I know that (and that's not the number of version which make the difference, see Windows :) ), I'm more asking for what added functionnalities consume so much RAM, and is it possible to disable those, or that would mean modifying the better part of the Firefox' code since they are implemented in the core. For example, I never use Firefox Sync, but this functionnality probably still loads unused code in RAM. "Why can't we have a core browser which just implement a GUI to a rendering engine, then add module on it for each optional functionnality ?" is more or less what I'm thinking. – piernov Mar 5 '14 at 20:27
Firefox is open source. You can grab the source, modify it yourself and create a lighter browser for your needs - but that of course requires good programming skills. Or you can simply switch to some lightweight browser. – gronostaj Mar 5 '14 at 20:56
Obviously you answer me that. I'd have prefered some "detailled" answer, like it was not done because of technical limitation, etc… I don't know many lightweight and convenient browser, Midori is one of them but I think that's all. – piernov Mar 5 '14 at 21:09
It's not really a browser or RAM consumption that's the culprit, but the fact that it's a 15 years old machine. It just won't handle modern web. You can try different things, like use a stripped version of XP or some lightweight Linux distro, but it will still be far from convenient and fast. It's just too old. – gronostaj Mar 5 '14 at 22:00
I know that this hardware is way too old to be used daily. I could upgrade the RAM to 512MB, or maybe 1GB (I don't think the motherboard support it though), but that wouldn't help much with the other specs. (can also replace the CPU by a 1Ghz one, but still) GNU/Linux will surely help there, but the browser problem is the same. I will maybe give a try with Midori. I've a few other Pentium III, would like to see them being still usable. – piernov Mar 5 '14 at 22:19

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