So, because of one poorly designed shitty website you're moaning about FF being bad? You should be moaning about Twitter with its bliveted 8 tons of javascript in a 5 pount sack.

You can add espn.com, washingtonpost.com and nytimes.com to that list as well.

Blivetware.

It's a fair complaint when this doesn't happen on other browsers.

Your website doesn't have to have "shitty poor design" for it to lag FF. Compare scrubbing in this React player in Chrome and Firefox: https://hsreplay.net/replay/WpWzqzkCHTGdEmbguHUoiC

It comes down to issues in the Firefox JS/DOM engines.

The websites I called Blivetware are shitty on all the browsers I've tried. I guess it's truly YMMV...

In my experience, Twitter and ESPN can bring any browser to its knees

I'd rather a browser that can handle shitty websites than hoping every website will somehow magically be written efficiently. Especially since FF is the only browser I know of that can't handle multiple active javascript sessions. It's completely absurd if you think about it, I mean it's a browser, for browsing websites, which use javascript.

If I open 5 to 10 tabs with various twitter profiles loaded in them, and I won't notice much because of the icepick that I'll very shortly embed in through my ear.

However, I routinely run with tens of tabs open - usually 40-50 - and love the 'tab groups' extension so I can semantically group them (I have more tabs overall, but they're not all actively loaded). It can get a little slow with 50 active tabs, yes, but what doesn't? Modern webpages suck CPU and RAM dry.

Hmmm, this sounds like an interesting extension. Does it ACTUALLY unload them (and release the memory)? Well, even if it quit executing javascript, I'd be sold.

Ah, I've misled. I mean that I have a lot of tabs in groups, and FF doesn't load them when you start it up, just when you visit them. So while I have a 'map' of perhaps a couple of hundred tabs in those tab groups, only the ones I've visited in that session are loaded.

The same happens for me in Chrome. Twitter is the issue, not your browser.

Chrome tabs each have their own process though, so then wouldn't your problem be your PC?

Sure. But if three instances of a website can bring a fairly new machine to its knees, then there's nothing any browser could reasonably do to fix Twitter's massive JS bloat.

In my case, FF uses well less than 10% of CPU, yet the browser is extremely unresponsive. So no, it's not the machine, it is FF.