> I have been searching in vain for something like that: stop scripts in background tabs except for specifically whitelisted pages.

Have you tried UnloadTab?

https://addons.mozilla.org/en-US/firefox/addon/unloadtab/

Ok. Will try. I think I see an issue here where I want to go back to a tab I have open on the train home.

If it is unloaded that means I have to connect to the Internet again to get hold of my page again?

(I'd think what I want is just to pause any javascript or other processing from any webpage that us not focused in the browser and not specifically whitelisted.)

Background tabs already have their timers run less frequently. In Firefox, that was added in 2011 [1]. Certainly further improvements to reduce background tab activity would be nice. One way you can sort of get that effect is to use Reader Mode, on pages where that works.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=633421

Or you can buy 2GB of RAM with those $30

We've reached a point where a lot of consumer hardware simply can't be upgraded. The ideal of just adding more RAM isn't possible (or perhaps practical in many cases). MBPs can't be upgraded at all these days. My Lenovo laptop can, but going 16 GB -> 32 GB requires far more than $30 since I'd need to buy 16 GB SODIMMs.

That's also a bit beside the point. I have a workstation with 48 GB RAM. I left a browser running in the background and had one tab consume 20 GB on its own before I killed it. Many of these leaks seem to just be unbounded memory growth, so that hypothetical 2 GB you add is going to be eaten up in short order anyway.

The scenario you describe with one tab using 20Gb is "beside the point" and certainly an exceptional situation. I've never seen that happen... I think I've had one Firefox crash this year, and that time it wasn't using all the RAM - it was hogging 100% CPU instead.

Of course the extra 2Gb might help for someone with less than 48Gb in their machine (most of us!).

Well, my point more was apps/sites that go sideways will eat as much RAM as they're allowed to. The 20 GB case was only special in that the leak rate was much higher than most. On a smaller scale, whenever my laptop fan kicked on, I knew I left a Travis tab open in the background somewhere. That was the CPU going into an aggressive GC loop due to the relatively huge amount of memory being used (2 - 4 GB).

But my original point is really that dismissing gross memory usage by saying you can buy more RAM for cheap is no longer accurate. In many cases, your machine's configuration is unchangeable. Getting an extra 2 GB RAM isn't $30, it's the cost of a brand new device. In other cases, where you might have configurable hardware, you often have to buy the largest capacity chip available and the economics get skewed. For SODIMMS, going 8 GB -> 16 GB is reasonably cheap, 16 GB -> 32 GB is fairly expensive.

I'd argue having to do a hardware upgrade for a web app in the first place is a bit silly. There's often very little reason for these apps to be so large in the first place.

It's not the RAM for me (I have 16GB).

It is about things like harrassing my CPU multiple times a minute after my search results have loaded (looking angrily at you googlers, google was the worst offender here it seems! (Windows 10, FF))

More memory doesn't help. I have 64gb and still need to close ff every few days. (Granted I do keep 50-100 tabs open at all times).