(Double edit: thought I was writing a redundant review but it turns out listing ones reviews in ones profile it doesn't tell you WHAT the review is of...HOWEVER, getting to "CONTAINERS IN FIREFOX..."

TL; DR version:
Like:
Moderately highly recommend as a "why not should help not hurt" additional layer of privacy defense, and has features that become semi-automated so it can be integrated into your workflow without much effort.

Would like if:
I'd like a little more customization (UI) and as a non-tech person (I only know a couple things) I would like to underrstand more of the "UX" lol, but while no one is perfect, this extension (literally) of a "non-profit seems like a no brainer though unclear how MUCH it helps it's easy to use.

The TL;DR "more"
Seems to do what it says it will do (in the background) well, and/or perhaps it's simply extra layer of defense I think at minimum? One thing I don't like is not being able to change the primary categories...you can add additional containers naming them anything you want, and I HAVE done that for a couple. They limit the number of symbols and colors you can use for each container which is only slightly annoying ;-) I LOVE how I set it to "open new tabs in a container" and it brings it up and you choose so don't forget, and how it automatically opens different web sites in the asssigned container (it asks you "always open in this container?" which is also a nice workflow/don't have to remember thing. These days things are so complicated that between the native browser protections, additional settings, add ons like this, etc, it can be very difficult to figure out if something doesn't work on a website where the problem is. That seems to be a rare problem though and I've worked around it and don't know that ANY were from this extension. The click symbol to change to a container is also eay to use/find. This seemed like a "no brainer" especially with the objects-in-libraries-associated-with-appearance-of-person-company company who along with those that had one strange rule and couldn't keep it strangely which has many services including finding things on the web, the container thingee is relatively simple and seems to work well not that I can tell what's going on under the hood but file under "probalby helps; doesn't seem to hurt or if does hurt not much at all!"

Very good add-on, 6 points from 5

I have Firefox 109.0.1.

Firefox Multi-Account Containers 8.1.2 can't open links outside of any container from the personal container if user made 2 confirmations... Links will open inside the personal container instead. It's not clear if there are any hidden settings around this. I don't think that manual requests from the context menu should follow the general rule, they should be given priority. Left clicks and the address bar must obey the rules, but right clicks must take precedence over the rules.

Firefox Multi-Account Containers 8.1.2 will ask for confirmation twice when assigned and then when opening any website.

By default, Firefox Multi-Account Containers 8.1.2 doesn't have even the largest banks...

By default, Firefox Multi-Account Containers 8.1.2 doesn't have even the largest marketplaces and shops. Users have to add shops manually... Definitely not suitable for smaller shops.

It's not clear how to create more than 4 containers or rename the standard ones with Firefox Multi-Account Containers 8.1.2...

It's not clear how to clear some or all containers with Firefox Multi-Account Containers 8.1.2... Users don't have visible options.

Absolut unverzichtbares Tool und Alleinstellungsmerkmal von Firefox.

Truly helpful add-on. Love it.

I couldn't imagine using a browser day to day anymore without this feature.

To @daze who asked about changing stuff once it's set to 'always open'. Click on the Add-on int he toolbar, go to 'Manage Containers' > choose the container which was assigned and then select 'Manage site list'. You can then remove sites from opening. It would be nice if it could be disable temporarily.

Really useful for when you need it. But if you ever use the "Always Open This Site in..." feature, there's no intuitive way to make it open in a non-container tab. You're stuck with that shit forever. I'm so incredibly frustrated with this.

It presents a serious problem when starting firefox, it always stays 5 minutes without loading any page when having the container enabled.

Whoever came up with this is a genius!