I'm using Firefox Quantum (64-bit version) but it is still lacking many useful addons and crashes a lot more often on my system (Windows 7 64-bit) than Firefox's previous version (I was using 32-bit Firefox setups before Quantum).

I'm thinking about "going back" to the latest version of Firefox from before Quantum revolution.

My questions are:
1. What version is it?
2. Is it still somehow supported with security (and other) updates?
3. Are non-Quantum addons still developed?

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Edit: TL;DR of responses I've got so far:

- There is no still Mozilla supported version of Firefox with legacy extensions support.
- There are some forks of Firefox which still support legacy extensions (like Waterfox and Pale Moon) I should try.
- Mozilla is going to remove legacy Firefox extensions from their portal for extensions in early October.

1. 56
2. No. Not even the last pre-quantum ESR, 52, the current ESR being 60. Doesn't stop me from keeping it, hardly use it anyway.
3. That I don't know.

Wait a sec - so 52, 56 or 60 is the latest non-Quantum version? So are you a Chrome user?

Firefox 57 dropped support for pre-quantum extensions. Firefox 52 was an ESR series, which remained supported until September 2018. As a result, it was actually supported longer than the newest non-quantum Firefox (56), which ceased receiving updates in November 2017 because it was not an ESR. There are no upstream-supported versions of Firefox which work with pre-quantum extensions, which is why a substantial number of Firefox users are now running insecure and known vulnerable versions of Firefox. Such users have decided that their workflow, with pre-quantum extensions, is more important than the improvements in Firefox Quantum. This is driven in large part by how many valuable extensions have not been updated to the Quantum "WebExtension" model; many extensions simply cannot be updated at this time because WebExtension is completely lacking the required integration points.

Last regular non-Quantum version was 56, but the ESR at the time was 52, replaced since by 60, which is post-Quantum. IE. So, ya know, basically unable to use GOG bar the forums since the redesign. I had actually finally gotten around to install Vivaldi shortly before that hit though, so could see how it should look and know why it sucks even when it does work as intended. Tried Vivaldi while I used Linux for a few weeks 2 years ago, thought it checked plenty of the right boxes, but kept edging away due to it being based on Chromium and me wanting nothing in any way related to Chrome around... But eventually gave it another go... Still misses a few things I still prefer IE for (high on the list being just that it's stable and just gets security fixes and I don't have to wonder what the heck they'll change / break next with all the darn rapid release schedules now) and fonts look just terrible, no way to use it at length and read stuff, not at regular size at least, so just there to replace FF in case something doesn't work in IE, which would be GOG now...

Yes, I'm so missing TabMixPlus. :( Well, so it seems there is no good way to go back to my old extensions and feel secure at the same time. :/

Give Waterfox a try? I switched on linux after they killed 52.9.0 ESR. Supports older addons at 56.2.3

I use Quantum on Windows tho.

EDIT: I really appreciate the performance improvements of Quantum, but I would trade it back for the amazing collection of add-ons that got left behind >:( + I can't stand the fact that add-ons each have their own interface now since they can't use the stock layout anymore. It looks and feel awful...

EDIT2: Added example of the terrible way layouts are handled now....

EDIT3: I just realized it's synonymous with the changes on GOG's website XD

I get that, waterfox is probably the closest, or possibly Palemoon, I don't think it adopted the Quantum update.

The downside though is that pre-Quantum Fx based browsers in general are likely to have poorer support due to having fewer users and fewer developers.

I'm missing NS option to Revoke Temporary Permissions on the current page only. :/
New NS version does not have it and it was commonly used by me. I was tempted to try "other Firefoxes" but then I've found this and that stopped me a little. :(

That's more or less what I was getting at, those other options just don't have the resources to keep pace with security issues that crop up the way that Firefox does.

It's really a shame that the people running Firefox are such morons with their UI destruction. Quantum was more or less inevitable at some point, Chrome and other browsers that do an entire browser instance per tab use an obscene amount of RAM.

Interesting read! But really? That's their excuse? 1-2 weeks for a security update? I can live with that. I was expecting some kind of conspiracy going through that article, but yeah I'm still just testing it out. Though It looks like I'll be staying on Waterfox on Linux for now, been using it for a few weeks.

Like I said on Windows I moved to Quantum, but delays in Waterfox updates are to be expected. It's in the nature of the application. It's a good trade-off at the moment for older add-on compatibility.

EDIT: Grammer? no Grammor? Yeah Gramir...

All working fine here, hehehe. Yeah, saw that on the addon page. It looks, again, something more for mobile rather than desktop use. Ghostery is another addon that had a terrible layout change at some point (that was before Quantum though, I think). Same here. Looking at the picture, you would have to "click" on the default option for that, I guess?

What do you think about it? Can you see any more cons vs Quantum? (beside delayed updates)

Same here. :( I used FF 52ESR on all Windows+Linux systems here until support ended for it not long ago, then very very begrudgingly updated back to current consumer grade Firefox Quantum to ensure security is maintained. Along the ride many of my addons that did not have Quantum compatible versions did finally come out with a Quantum release, and I found alternative Quantum compatible addons that either were comparable or in some cases better than prior non-Quantum addons I used, but also have experienced great user experience loss where addons I relied on both never got updated and there is no other viable comparable addon that is Quantum compatible.

Tab Mix Plus is my greatest catastrophic loss to date. They continue to work on a Quantum version of it but it'll be a long time until it is remotely close to on par with the last non-Quantum version of the addon due to limitations in WebExtensions that may take a long time to be overcome if they ever do.

There's a greater wake of missing addons that I suffer through for now, but hopefully throughout the next year the situation will improve again and we end up having our cake and being able to eat it too.

I was thinking in similar way "a year ago" when I migrated to Quantum. But "after a year" of giving the chance (and seeing not the great improvement) I think this loss is kind of "too big" to not try some other alternative.

Especially when Quantum, to my experience, is "not so stable on my system" as previous editions of Firefox and I do not know what is it (maybe it's 64bit or my Windows 7).

Have you thought about any other Firefox's fork like I do now?