I really enjoy the ability to isolate sites with containers. Works great if you want to be logged into multiple accounts on the same website. Two or more gmail accounts open at the same time.

This functionality is wonderful when doing web development. Testers/developers can be logged into all the website roles at the same time if desired. Great when used in combination with https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/

Best solution I found for managing multiple AWS accounts simultaneously.

This is a fabulous concept, and it works well. But it is missing a key feature that I have come to expect in my Firefox experience: namely syncing. The setup of containers should be able to sync between the Firefox instances in my Firefox account, just like add-ons and regular preferences.

Excellent Add-on, a must have! It would be fabulous to have an android version as well.

Must have extention

Ok in the desktop browser but pointless when the iOS does not support extensions, so will go back to using separate browsers to separate out my work and personal profiles.

Best innovation in browsing in a long time. Combined with Temporary containers is an amazing combination.

Please, add synchronization of containers

This extension worked fine for me before. But since one year my different conainters don't remember my 2 gmail accounts, so i'm forced to relog each time. Reinstall of firefox doens't solve the matter.
If someone has any other advice or other extention to recommend, i'm all ears.

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THIS WONT WORK (THE EASY WAY):
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Misleading quote: "Avoid leaving social-network footprints all over the web (for example, you could use a Container tab for signing in to a social network, and use a different tab for visiting online news sites, keeping your social identity separate from tracking scripts on news sites)."

You'll need to add an option to change its behavior. When opening a site in a container (e.g. Bing-search) - clicking a link - the new (unassigned) site will stay in the same container thus enabling tracking. Pretty useless this way. Although useful for using different profiles, it's not secure/private.

Options to add (user-decided behavior):
- Open new unassigned sites in the default container, a temporary container or current container (you can reassign later)
- Switch/assign (via toolbar button) the current site to different container (assign/move/copy to a new container for site)
- Changing to a new container will open a new tab or use the current tab (a new tab to avoid losing *cursing* history)
- Option to open web sites in their own containers without the user assigning a container (auto-created for TLD's) *
- Possibility to select a default container for a site assigned to multiple containers or use last container used
- Possibility to sort container labels
- Add an overview of which site/data is contained in which container
- Try to also use the omni-box for extra functions (assigned container switching) since the container-label is already there

* When reassigned by user the auto-created container is renamed or merged with an existing container

EDIT 1: Rating lowered from 2 to 1 star until problems are solved. Totally wrong implementation (the omni-box becoming useless and is imprisoned by this add-on). I get the idea but it's wrong. Visiting Facebook, then entering a different URL, will keep you in the Facebook container. Track-track-track. Just too much concentration and handling is needed to keep things real secure. For now this extension is just a kind of identity switcher within the same Firefox user-profile. Why not then just create an add-on to switch to another user-profile with a toolbar drop down-menu? At least that's clear and transparent. This surely isn't! For this to work properly you've to create a container for every URL/cluster of sites you visit. We need Firefox Web Clusters/Containers.

EDIT 2: Found out that sites are currently not even linked to containers (only cache/cookie data) which was not my assumption. It starts your selected container and stores data in that container separating data from other containers. The problem here is that selecting a default container for a specific site results in not being able to switch accounts for that specific site. A contradicting (dis)function.

Abstract/Résumé:
- You can switch profiles by selecting containers in the toolbar-button (entering the URL again)
- Ones assigned to a specific default container, you can't switch profiles
- You'll need to be careful entering websites you're not willing to have in the container since this enables tracking *
- To protect you from tracking you'll need (an) extension(s) that isolates Facebook, etc. from all other containers **

* You'll notice you're logged off from web sites (don't log in but start a new container). This extension is (not) for dummies.
** There's a Facebook container that doesn't work i.c.w. other forks (Google, Twitter, etc.). Also you can't switch profiles.

EDIT 3: For a workable solution install these extra add-ons

- Switch Container (https://addons.mozilla.org/en-US/firefox/addon/switch-container/)

- Temporary Containers (https://addons.mozilla.org/en-US/firefox/addon/temporary-containers/)

Moz://FifthAxiom