There is a feature called First Party Isolation that (I think) does what you want for normal tabs, and can already be enabled through about:config. (initially developed for the Tor Browser Bundle, their description of it is here https://www.torproject.org/projects/torbrowser/design/#ident... )

Thanks for that. Found it and enabled it.

privacy.firstparty.isolate

Beware that privacy.firstparty.isolate might break some sites that depend on third-party services for login authentication or comment systems. If you find any broken sites, you can report them in Bugzilla and mention this Firefox bug:

https://bugzilla.mozilla.org/show_bug.cgi?id=1299996

I use noscript to by default turn off scripts from 3rd party sites (unless whitelisted). It breaks quite a few sites, but it also makes lots of sites load quicker and doesn't load a bunch of advertising/tracking stuff that I don't really want loaded anyway.

I would pay actual money to help get a feature like that into Chromium or Firefox. Hell, if Firefox added that exact feature I might actually rethink my decision to switch to Chrome once they drop support for all the addons I use.

There is an experimental implementation of that feature, called "First Party Isolation", in Firefox today. You just need to set the `privacy.firstparty.isolate` pref = true in about:config.

With this pref enabled, advertiser X will serve you different cookies on site A and B. They won't be able to track your browsing history from site to site. However, this breaks a lot of sites that depend on third-party services for login authentication or comment systems.

Here is the Firefox bug where you can report broken sites:

https://bugzilla.mozilla.org/show_bug.cgi?id=1299996

This would actually be implementable with the new WebExtensions for containers https://developer.mozilla.org/en-US/Add-ons/WebExtensions/AP...

Essentially building a new container per origin.

We are also hard at work supporting add-on authors porting to WebExtension APIs. I'm especially trying to help Privacy & Security add-on authors.

uBlock, NoScript, Self Destructing Cookies. Also DisableWebRTC. Firefox would be Opera, Chrome or Vivaldi without them. No particular reason to use it or a random one among the others. Stylish and Greasemonkey are useful too, when sites insist doing the wrong things. I hope all of them survive the switch. Will they?

You can keep track at https://arewewebextensionsyet.com/#addons

uBlock Origin started as a Chrome extension.