Hi all,

I use Firefox on several Linux Mint desktops. Time and time again desktop performance degrades and it is almost always firefox using 100% CPU.

I understand modern web pages are complex. I understand Javascript can be slow. I understand that some pages do crappy stuff like running autoplay audio or video.

What I don't understand why any page in a browser needs a lot of CPU action once it has loaded a page, unless it is running complex animations or something.

At least Chrome runs separate processes and you can just kill the process hogging CPU. But why is the the page hogging CPU in the first place?

Please enlighten me, if you can!

Firefox periodically cleans itself up. If you wait the CPU usage should return to normal. But, a page can have a defective script that can hog the CPU.

if i understand you correctly, this is a problem with the webpage, and not the browser.
yes, some webpages/sites take insane amounts of resources, and some never stop loading. it's impolite, to say the least.
you can control most of it via noscript - disable javascript, and if the page doesn't load, enable just the bare minimum needed to make it work.
but still, some commercial sites will remain unusable until you allow almost everything, and they simply are heavy, bloated, resource-stealing...