H AHoff, Sorry you are having problems.

Using more memory is not always a bad thing. You have 16GB of RAM, and may benefit from trying out the 64bit version of Firefox. That is new and not offered as standard for Windows users, but Linux & Mac users have had it for years.

See

• How do I tell if I have the 32-bit or 64-bit Firefox? (Forum software detect you posted from 32 bit Firefox)
• How to switch from 32-bit to 64-bit Firefox

See also

• Firefox uses too much memory or CPU resources - How to fix
• Firefox uses too much memory or CPU resources - How to fix
• Quick fixes if your Firefox slows down
• Fix problems connecting to websites after updating Firefox

I would suggest you follow the steps in the article to Install 64 bit Firefox, but do NOT uninstall the 32bit version. Instead make sure you have a separate additional Firefox Profile for the new version.

• Profile Manager - Create, remove or switch Firefox profiles

Does the 64bit version work better ?

Using 15% of CPU should be no problem, and probably does not cause any slowdown.

On a 32 bit version of Firefox using 2.5GB could cause problems, however there could be other more important reasons for your problem and perceived slowness.

I am not too sure deleting content-prefs.sqlite would be expected to drastically change memory usage, maybe the effect is more from just closing and re-opening Firefox. Try closing then restarting Firefpox without deleting that settings file does that reduce the amount of memory apparently used ?

So we know what you are experiencing can you give some examples of what you mean by slow and unresponsive. explaining what you are trying to do and what you mean by slow - for example

• Do you need to wait 5 or more seconds to key in each letter whilst typing word into replies ?
• Does Video Freeze ?
• Do websites take minutes to fully load ?

Have you tried similar tasks with both Edge & Internet Explorer, how do they compare to Firefox. (Firefox should be a similar speed, maybe sometimes even faster).

Thanks for the quick reply. I haven't yet tried 64-bit Firefox, but I thought I would respond to your answer in the meantime. You are right that restarting Firefox, not deleting the content-prefs.sqlite file, is what brought memory and CPU usage down. Even without resorting to Task Manger, I can tell when memory and CPU usage has increased to high levels by Firefox becoming slow and unresponsive, by which I mean it is slow to respond to mouse and keyboard inputs: scrolling, typing, tab and text selection, clicking on links, etc. I often have to wait for the cursor to become active so I can click on a link. I've tried opening the same web page on both Firefox and Chrome, and didn't notice this behavior on Chrome, although I haven't given it a thorough test. I haven't noticed slow loading of websites or video freezes. Many thanks for your help - it's hard for a non-expert to understand why memory and CPU usage increase so much in the course of normal use.

I've now tried 64 bit Firefox. Rather than installing a second version, I put the current portable 64 bit version (50.1.0) on my data partition and copied my profile to the portable version. This gave me two versions of the program that are identical except for the 32/64 bit difference. I'm not seeing a noticeable difference when running the 64 bit version. It is possible that it takes a little longer for the 64 bit version to run up memory and CPU usage, but that is very subjective and it wouldn't be a significant difference in any case. I can still tell when memory and CPU usage has gotten high by the slow response to keyboard and mouse inputs. For what it's worth, I am also running an almost identically configured 32 bit Firefox on my other desktop, which only has 8 GB of memory, and I am not experiencing this problem to nearly the same degree. I would greatly appreciate any additional advice, as this is a colossal nuisance. Also, as a matter of curiosity, I would be very interested in knowing what causes this enormous increase in resource usage. Thanks very much.