Firefox 32-bit vs Firefox 64-bit

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I was excited to try the new 64 bit Firefox as I read the news that it was released as a final version. After all, I’m using 64 bit Windows for some years now, and browsers have been very late to release their 64 bit versions. Read on how I compared if Firefox works better in 32 or 64 bit and see the numerical results below.

I’m using Firefox with many tabs simultaneously open (around 80) and at any time there’s around 30 – 40 tabs loaded and clicked on in every session. I also try not do restart Firefox if not needed. Sometimes I have to do it because of a new Firefox update, sometimes because it crashes, and sometimes because it stops being responsive. That being said, Firefox is a huge resource hog on all my systems, by far the biggest. I have noticed much better Firefox performance after I upgraded to Windows 10. The memory footprint of Firefox before the upgrade grew up to 3-4 GB, but after upgrade it rarely reached above 1,5 GB. That made me happy because it also meant that I need to do less Firefox restarts to make it faster.

When 64 bit Firefox was released I wanted to test it and see if it improves on memory footprint even more. I have installed both 32 and 64 bit versions of Firefox 43.0.1 on a laptop with Windows 10 and only 4 GB of RAM (plus 8 GB of swap memory). I have used my regular Firefox profile and worked on each Firefox for some time.

After a few days of use the result that I saw already at the first run was confirmed. 64 bit Firefox was not doing a good job. There were no problems with the functionality, but memory footprint reported by Task manager was much higher than the one by 32 bit Firefox.

Memory footprint measured by Task Manager – Firefox 43.0.1 (32 bit): max 1,7 GB
Memory footprint measured by Task Manager – Firefox 43.0.1 (64 bit): max 2,9 GB

In fact, memory footprint was so much higher that I switched back to 32 bit Firefox for some time. I don’t know the reason for this, but I’ll be doing some more tests with the next versions and maybe Aurora. After all, 64 bit will be the choice of the future…

TIP: Are you running 32 bit or 64 bit Firefox?
If you’re wondering if you’re running 32 bit or 64 bit version of Firefox, you can find it out easily (but not as easy as it should be).

Option 1 (in Firefox):
Open a new tab and open about:support. Look for “User agent” data. If you’re running 32 bit Firefox, it will contain string “WOW64”, in my example the User agent is “Mozilla/5.0 (Windows NT 10.0; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0″.┬áBut if you’re running 64 bit Firefox, User agent will contain the text “Win64”, in my example “Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:43.0) Gecko/20100101 Firefox/43.0”.

Option 2 (in Task Manager):
Run Firefox. Open Task manager (you can open it by holding Win key and pressing X and then selecting Task Manager). If you see “Firefox (32 bit)” in the process list, that means you’re running 32 bit Firefox. If you see just “Firefox” it means you’re running 64 bit Firefox.

What are your experiences with 32 bit and 64 bit software? Does Firefox run faster? Please share in the comments.


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