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We use different AWS accounts for different purposes at work. It would be an extreme productivity loss if I had to go back to using something other than Firefox's containers.
It's not an identical feature, but I have some workflows which require Chromium and compartmentalization between a multiple accounts, and Brave's profiles aren't a bad alternative.
For someone that hasn't used Brave in a while - what's the difference between Brave profiles and profiles in other Chromium browsers?
There may be other Chromium-based browsers which do this, but none that I use: on launch the user is (optionally) prompted with a profile selection tool, with additional options to create a new profile or go into a guest session. I appreciate this because without it I often end up wondering why something isn't behaving properly, and after a moment of confusion then realize I'm in the wrong profile.

It's not perfect, and I prefer Firefox's rules-driven containers, but for anything which requires Chrome I've found it sufficient.

Ah, that sounds nearly identical to the standard launch-time profile picker from the Chromium base - example from Chrome https://i.imgur.com/7b7YqUY.png
Sure is, thanks. At the time I settled on Brave for that use case I saw no such behavior from any of my other Chromium-based browsers. Either Brave upstreamed it, or I did something wrong on my end (likely).
Pretty sure the setting has been around for a while, possibly upstreamed from brave but I feel like it was around before then. It’s pretty hidden tho, and most ppl don’t want it and get confused why it even exists so it’s possible there isn’t great documentation on it.
In Firefox this prompt is invoked with "-P" argument.
Chrome itself has profiles, which I use for exactly the same use case (multiple AWS logins)
You're correct. It does, but the last time I tried it it does not prompt on launch as Brave can, which provides a nice reality check for my addled mind.

I dislike certain aspects of Brave for other reasons, but this is why I have an unholy number of browsers installed and end up making use of nearly all of them regularly, unfortunately.

The Arc browser [1] could be nice alternative as it handles profiles pretty smooth.

[1]: https://arc.net/

This smells like pure marketing, incl the company's website. I'd rather use an open-source browser like Firefox.
Other than separate windows... is it very different if we use different Chrome user profiles to keep the saved logins, sessions, and cookies separate?
This does work. Not quite as nice as Firefox’s multi-account containers because tabs can’t co-mingle in the same window. But totally serviceable.

I use a combination of both every day at work.

I like chrome for some things too because you can make a single-site-browser window in chrome, so certain websites can be treated like first class applications in the alt tab menu.

> I like chrome for some things too because you can make a single-site-browser window in chrome, so certain websites can be treated like first class applications in the alt tab menu.

yes absolutely.

I did this for my local jupyter notebook server and pinned it to my taskbar. effectively works like a desktop app.

The amount of storage that these chrome profiles occupy on the hard disk is sometimes irksome. I have not compared it to Firefox though.

What would be needed to support this in private browsing mode? I would like to keep things separate and toss everything when I'm done.
Private browsing mode is essentially a new temporary container. It let's you keep things separate and toss them when you're done.
Yes, and I'd like to use more than one simultaneously.
Hi! Sorry to post here, but I couldn't find any way to contact you. You wrote here https://news.ycombinator.com/item?id=30301639 that you set up et and cloudflare tunnel. Can you tell me how? It doesn't work for me, et doesn't see an open port on the server.
Well I didn't mention Cloudflare Tunnel but to answer your question per https://old.reddit.com/r/selfhosted/comments/1128ce9/cloudfl...

1. Eternal Terminal does not support ssh_config ProxyCommand, so both tunnels must be TCP.

2. Cloudflare Tunnel TCP proxies through cloudflared running locally on the client. https://developers.cloudflare.com/cloudflare-one/application...

  #~/.ssh/config
  Host et.example.com
    Hostname 127.0.0.1
    Port 10022

  cloudflared access tcp --hostname ssh.example.com --url localhost:10022 &
  cloudflared access tcp --hostname et.example.com --url localhost:12022 &
  et et.example.com:12022
The following command must be run once to authenticate:

  cloudflared tunnel login
Thank you! I already gave up and just ssh to the server, but thanks for your comment. At least I figured out how the forwarding works.
The temporary containers extension is probably what you want. MAC is for separate but “permanent” environments.
Last week I finally removed some bugs from my multi-instance chrome scripts on macOS.

I basically have different applications of chrome, each with a different profile. They wacht have a different app icon, browser color, and extensions.

It helps me focus a lot to have a different application (cmd-tab entry) for dev, media, general browsing.

Social media and other time traps are blocked on my general and dev browser.

Works very well I have to say. It copies Chrome using clonefiles (CoW on apfs) to save space.

The only thing is that updating goes through the main browser (automatic updates are buggy in this case). And I have to codesign when there’s an update, but the scripts take care of that.

Can anyone clarify what this provides compared to the built-in container support in Firefox? On stock Firefox, it appears that I can do everything listed in the documentation above, with the exception that this extension appears to allow you to configure a domain to automatically open in a given container. Is that the only difference?
This is the user interface to that built-in container support.
Mainly these two things: * Assign sites to a specific per container * Set VPN/Proxy per container
It is really just the eaiest way to turn on the built in container support.
Very useful if you have multiple Outlook accounts (e.g. school, work, personal), because outlook.com doesn't allow you to switch between accounts without logging out and back in.
Or you hop between different AWS accounts.
Or gcp or other Google products. They technically supports it by appending different authuser query params, but whenever you click something it's bound to choose the wrong one.
I still can’t believe you can only be logged into one. Also when I re-log in it shows all the tutorial pop up boxes on everything EVERY SINGLE TIME.
I tried to like this the other day but it was a real hassle.

I have 3 accounts on a website. I thought I could setup 3 different containers, one for each account. But it turns out that switching between containers is not simple. Whenever I tried to switch, I got a pop up from Firefox asking me if I was really sure I wanted to switch my default container for that website. Sometimes it sent me into a redirect loop with the prompt also. I did some googling and found that the consensus was that containers simply aren’t meant to be used that way.

Firefox Multi Account Containers seem to assume you will always use one container for one website, and you can’t easily use multiple containers for a single site. Or at least, it’s very inconvenient to do so.

Ugh, same. I thought I was the only one that found these to be impossibly buggy.

The container setup/management UI is glitchy and it often forgets! containers that were created. It feels like a hack week project that got shipped to production.

Despite having containers, Firefox sometimes wants to open the managed website in your current window. Or doesn't ask you at all when you have multiple containers for the same site.

There's a lack of distinction between containerized / non-containerized windows. The colored tabs do not work or break down, leaving you in a mysterious or even dangerous state.

The integration with password management tools is obviously rough. But coupled with the browser's own attempts at session management, plus containers, it's a UX nightmare to log into the right container.

The last time I checked this out was last year. Maybe it's better now? Given Mozilla staffing, though, I'd guess not.

I really want this to work, but the current solution is worse than none at all. I've made do with keeping multiple browsers for different tasks.

Be careful if you use this. It breaks unexpectedly and that can lead to the wrong actions being taken in the wrong accounts.

The struggle is that the container addon does its own syncing, separate from the browser-wide Firefox account sync (that decides the soon should be installed).

Because syncing is a separate step - yet it still happens concurrently/unpredictably in the background - there is no avoiding the default new user flow that creates 4 default containers at install.

I mean there is if they'd fix it :) . Don't sync those 4 if they already exist, don't sync at all otherwise. I would assume if you are smart enough to use sync you're smart enough to know that it will blow away old "local" settings.
The tool needs to get out of the way. People are busy and have a million other things on their minds. Grappling with an obtuse, broken product is a hurdle.

As it stands, Firefox containers are 10x more complicated than regular browsing and it exposes sharp edges.

>>The container setup/management UI is glitchy and it often forgets! containers that were created.

been running it for years, never once has it forgot containers...

>>Firefox sometimes wants to open the managed website in your current window. Or doesn't ask you at all when you have multiple containers for the same site.

ok, so you right click and have it reopen in the correct container, not a big deal. Though I cant say I have ever had this problem either despite using it very day all day, 16 hrs + per say with lots of containers and tabs (often over 100 tabs open)

>>The integration with password management tools is obviously rough.

I use bitwarden, have no issue using it inside of various containers

Interesting, I accomplish this just fine and it's my primary use for containers in Firefox. I don't know what your workflow is like, but I just click the "+" tab button, select one of the other containers I want, and a new tab opens in that container. Type address of website and continue as normal.
Wait; what's the point of them if they're not meant to be used against the same site?!
They are. My guess is that person is doing something wrong.
The feature is incredibly buggy. I wrote a sibling comment that details some of the glitchiness.

It's dangerous to use a system that can't keep sessions independent. There are bugs that may cause you to inadvertently take action in the wrong account. I nearly botched one of our own accounts.

To isolate the cookies and JavaScript of a domain from other domains.

For example, Facebook is notorious for reading third-party site cookies and vice-versa. A collection of associations (X Facebook user visited Y sites) is then sold as a portfolio for targeted advertising.

I agree this isn't the feature that provides the most utility; it's simply the one that was originally at the front of the devs' minds.

isolation of cookies and other data between websites. although now I think firefox does that per tab anyway&site combo nowadays anyway. I mainly use it for multiple reddit accounts and gmail accounts. also good when combined with cookie auto delete for test purpose between testing site changes "freshly".
I use mine for organization (all banking sites are separate from shopping websites) and to cordon off toxic sites like Facebook.
What you're describing is the main use case for this. Are you sure you're using it correctly? You're not supposed to change default container for that webpage all the time or anything like that.

I for instance have a bookmark for a page. I right click it and select which container to opening it in. I often open it in different containers, have different tabs of it open at the same time etc.

I went through the same process when I tried it a few weeks ago for multiple GitHub accounts.

I also uninstalled the extension after fumbling around with it for 5-10 minutes and not being able to open multiple containers of github without it forgetting what I just tried to setup or constantly bugging me about switching the default container.

Based on some of the comments, maybe I'm "holding it wrong." I don't know, but I spent a good 20-30 minutes trying to get this sorted out before deciding it wasn't worth the time.

Love Firefox, and I like what the Multi-Account Containers are trying to be, but it just didn't work for me. And it sounds like I'm not the only one who's run into this issue.

Unintuitively, you want to have no default set for that domain, and you want to open an empty tab of that container type (by long clicking the new tab button or clicking the container addon button itself to get a list). Once you have a container open, middle-clicking the new tab button will open an empty tab in that container.

I agree that the UX is horrendous. Most of that is a byproduct of implementing it as an addon instead of a feature.

I think this only happens if you use the "Always open this site in container" function.

I use MACs with a bunch of different AWS accounts for work, and the only papercut is having to right-click my bookmarks and choosing which container to open the console in (as opposed to having MACs integrated with bookmarks themselves)

You absolutely can. Open a new tab of containerA and login. Open a new tab of containerB and login with a different account. I think there's an option somewhere that allows you to select "always open [website] in [container]" which might be triggering that popup.
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Great for testing logins on web apps. I used a FF plugin to do this, I presume having this in FF itself natively is new.
I've been using this since it was new. I'm very frustrated to say the UI/UX hasn't seen any significant update.

Containers are still synced separately, so any fresh install of Firefox will have the tutorial UX and the default 4 containers, even after syncing.

Also, address bar completion is still monolithic, making it very easy to accidentally open a site in an undesired container. That can be worked around by adding every domain to a default container, but most of the utility of containers is to use several for a single domain, i.e. multiple email accounts each with their own container instances.

Containers are a feature I find very valuable, but they really need their UX to be a core browser feature, not an addon.

container sync has been a thing for a while, but you have to enable it: https://i.imgur.com/UBj3TjW.png
Where do you find that at? I just looked in both the Sync settings and Container settings and I do not see that setting.
It might be always-enabled now. Either way, containers sync is a separate event that can't be triggered manually.
Yes, and the flow is as I described.

1. Install Firefox.

2. Log in to fresh Firefox instance.

3. Let browser-wide sync happen.

4. Sync installs multi-account containers addon.

5. Four empty default containers are created. New user welcome flow is active.

6. Sign in to multi-account containers addon. Wait for container sync to do its thing.

7. Containers sync invisibly in the background.

- Default containers that you deleted before (in the instance you are syncing from) still exist in this fresh instance.

- New user welcome UX is still active.

Also....for me. At one point a janked up Firefox instlal on 8.1 created something like 100+ duplicates of some of my containers, specifically ones names TEst and Test2.

So each time i setup a new browser and sync then, i have to go through and manually delete all the duplicates.

They dont re-appear once deleted and changes still sync (ie: if i add a URL rule to always open in x container) but holy crap is it annoying.

This happened to me many, many times. Luckily I'm able to track down containers.json and remove them that way.

It also would never sync to my laptop for some reason?

The overall bad syncing experience was the main reason I stopped using them.

ya know.....it never occured to me to really track down the json file. Even though i totally know firefox really loves making use of them. Even had a sanitize script at one point that would kill any session on my work computer nightly and scrub my history without logging me out of sync account at a previous job.

I dont setup a new machine all that often that I care too much. I figured it was a misconfigured cloud DB point, that at best I could get Mozilla to clean up and let me re-sync, but even then didnt bother to open a ticket.

There is a json file with the containers, I also had a similar problem (temporary containers extension “leaked” containers and they got synced) but after having found that file (I believe it was containers.json or something similar) and manually removing from that all the bad elements I managed to get those out from syncing it to new instances.
Also, the order of the containers isn't synced properly. When you have a few containers, it's helpful to have container configured in the same order on every device you use.
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Agree, it's also quite awkward to link a domain to a container, and sometimes it doesn't work well, for example gmail because it also uses Google.com (I want to separate Gmail and my Google search)
You can open a bookmark in a chosen tab via the context menu when right-clicking on a bookmark in e.g. your toolbar. I use this to separate Gmail accounts. I use private search for Google search.
it also has about 3-4 different UIs, all of which have very slightly different options

brilliant functionality, just the UI is beyond awful

Is there a good native way now to set up url patterns (domain, sub domain, regex etc) to open in a specified container?

I've been using a non add-on store addon for this.. and no idea why something basic like that would not be in the core or this add-on

I am not sure what you mean by non addon store addon. Containerise is on amo and supports glob and regex patterns.

https://addons.mozilla.org/en-GB/firefox/addon/containerise/

Why do we need this?

I'd have every tld on it's own profile and allow creating groups that merge profiles if needed.

Have tried that - but the patterns there aren't case insensitive (and no way I could find to make them so); the one that I use is a fork of containerise - search for bifulsushi on bitbucket
I use Containers with Transitions (https://addons.mozilla.org/en-US/firefox/addon/containers-wi...)

It's a bit tedious to set it up at first but it's the only way I know of to get the following functionality:

With GMail open in a "google" container, non-google domain links open in non-google containers (configurable which container if any). Google domain links (drive, calendar, maps, etc) open in the google container.

Once setup, this means in your "standard" or non-specified container you can log out of all google services and stop their most explicit tracking of you through simple account cookies being read across the web while you search, etc. No longer when you visit sites that allow sign-in with google will your account name be auto-suggested, because the sites don't have that level of tracking info when you're browsing and searching outside of the google container. Viewing random trash yt videos will no longer sway the recs you get in yt.

The downside is that my google searches, done outside the google gulag, run into captcha prompts b/c I guess google search doesn't expect that much consistent traffic from someone who isn't signed into one of their services.

edit: this also means that you can, for example, containerize gmaps and set it up so that non-google domain links followed out of maps open in a non-google container. clicking a link to a business's website from their gmaps page no longers propagates your google account cookie to their site, etc. it opens in a different container, automatically.

You don't like the UI? It feels like a core feature to me, the only serious friction I have is that I also use temporary containers which overrides my selection to open a certain site in a particular container.

But you just tell it not to open a temporary containers for that domain and you're good.

So really I've only seen this take much thought when combined with temporary containers.

Sadly the Temporary Containers extension seems abandoned at this point. No updates in two years.
I had similar complaints about the UX for the built-in containers extension, so as a labor of love, I wrote a helper extension to make containers a little more intuitive:

https://addons.mozilla.org/addon/containers-helper

The simplest improvement is that you can use e.g. Alt+Shift+D to open a little popup and start typing to find your container(s).

You can also use the extension to import and export containers, as well as some other features.

The extension respects your privacy completely and is not programmed to make any outbound network requests.

This functionality seems to be partially included in the official extension now. There's a "search container name field", but it's not active when you open the pop-up (hence the partial).

I don't know when it arrived, I'm pretty sure it hasn't been there too long, but I don't pay too much attention to this extension's UI. I'm running Firefox 109.

It landed about a month ago. I'm the contributor who implement this patch and I already have another one in the work that would let you focus the filter box when you type "/".
Mozilla is on Googles drip. You can't expect this feature seeing much love it's against the donors intents.
And that drip is just as important for google to avoid an insanely huge monopoly lawsuit, so this is just the usual shitting on certain open-source projects without any reason.
How true is that these days? I see it mentioned a lot. Google doesn’t have to keep them afloat just to avoid some hypothetical anti monopoly issues.
Truer than ever. What other browser engine is there beside safari on macs? Not even Microsoft found it worthwhile to maintain an independent browser engine - in this world firefox is an open-source gem and instead of bringing it down for whatever reason we should try to preserve it.
Google is currently facing a search monopoly lawsuit where their payment to Mozilla is being used as evidence against them. If they were funding Mozilla to prevent a browser monopoly, the strategy certainly backfired.
Not the parent poster, but is criticizing a browser I've used steadily since it became a thing for letting itself become primarily funded by it's largest competitor really "shitting on it"? Do you really not think there is a conflict of interest there?
Fortunately there are some cool extensions that do improve that logic. My favourite uses a new container for every AWS SSO login, so I can have multiple AWS accounts and/or roles on the go at the same time.

https://addons.mozilla.org/en-US/firefox/addon/aws-sso-conta...

But completely agree, this should be a capability. It's like how Google Chrome profiles don't have the "open in another profile" menu option until you have two profiles already opened.

the container is definitely synced at least for over a year. since I bought my laptop last year and everything is synced
Firefox MAC is one of the first extensions that I install, after uBlock Origin, Privacy Badger, and Cookie Autodelete.

I install MAC despite my dislike for what the UI has become.

The UX was fine until Firefox started pushing its VPN service via this extension. I encourage the use of VPNs, that isn't my objection. But now the installation of MAC requires too many clicks just to configure it, and some of those clicks are to dismiss things that I didn't request.

Good UX practices:

    1 = offer reasonable defaults

    2 = be visually intelligible (make it easy to recognise borders, boxes, controls)

    3 = make it easy to access important properties (don't bury or hide what people need)

    4 = don't be annoying, nagging, exhausting, or confounding

    5 = favour exposing features in an organised way

    6 = let the user customise
The MAC extension suffers in points 2, 3, and 4 during installation. Now that Firefox has forced the grouping of all extensions in an Extension folder that cannot be moved, we now have a problem with point 6 too.
You can still pin an extension to the toolbar and if it's already pinned Firefox will honor your setting in Fx 109+. IIRC, we can also in the extension manifest.json force the addon to show in the toolbar by default.
Pretty useful. Something I learned at some point was that you can actually combine this with Wireguard: If you dig into the extension, there's a feature that lets you set a SOCKS5 proxy for a profile. You can then point it to a running Wireproxy to go from SOCKS5 to Wireguard. Could be handy.
@jchw that's neat! You've seen this in source or is it accessible somehow from the UI?
Accessible via the UI: click into the extension, click the right arrow next to a container, select "Manage This Container", then "Advanced Proxy Settings" and you can enter a SOCKS5 URI. And of course, this requires the aforementioned extension, not just the built-in container tabs feature. (Confusingly, Firefox does have this feature "cooked in", presumably they just expose a bunch of it via WebExtension APIs so that things like Multi-Account Containers can work.)
Also look at FoxyProxy which can enable unique proxy configurations on a per-domain basis
I've been using this for a few years now and love it. I wish for two things.

1) i wish there was a way to automatically delete cookies/cache/history from specific containers every time. My personal container needs cookies and logins saved. My other containers don't need persistent cookies.

2) I've always wished for protonvpn to apply to only specific containers. Reading this now though, I see firefox's VPN does that so that's very cool, I might need to look into their vpn.

I combine containers with profiles to achieve this... I have totally separate profiles for: 'temp' (delete everything on close) 'shopping' (containers for my common stores) 'finance' (containers for banks, etc)

Gives a lot of flexibility, and I'm a lot less nervous opening stuff in 'temp' session when I know everything else is safely in totally different profiles/directories.

What you want is the Temporary Containers addon: https://addons.mozilla.org/en-GB/firefox/addon/temporary-con...

It will let you open containers that trash cookies on close. You can also set certain URL's to always open in a tmp container which is useful for sites that only let you read x amount of article per month.

How is it different/better from incognito mode ?
incognito shares state between tabs. temporary containers can have a fresh container for every tab, so your tabs are isolated. you can also use it in a way that by default every site you visit is using a temporary container, with certain urls set to use their corresponding long term containers -- if i go to github, it opens in a github container, if i click a link to some random dev's site, it opens in a temp container, etc.

to provide context, i still use incognito, but i consider incognito mostly about hiding things from myself -- i use it almost exclusively for porn, because i don't want my porn habits in my browser suggestions. temporary tabs still land in the recent urls and such.

You keep your browsing history for one but clear the cookies out after automatically.
Incognito isn't as private as the name suggests. I was surprised one day to open a tab in Incognito and see the site I visited knew who I was. That's because I had logged in to a related site in a tab I'd forgotten about in another Incognito window.

My assumption up to then was that each newly opened Incognito tab or window was it's own private session, but this turned out to be wrong - they all share state, as if you had one separate but shared profile called Incognito. This was a little upsetting as I'd been using Incognito for years without realising the data sharing going on.

Temporary Containers does what I'd expected from Incognito. Each new temporary container has its own isolated cookies etc from all the others. So now I open a TC when I want to visit a site without identity or tracking, or to login temporarily with a different account, and don't use Incognito at all.

For what it’s worth, Safari’s incognito mode works exactly how you described it — separate session for each incognito tab/window.
So you can't open two tabs for the same site and share the session between them?
Correct, not in the private browsing mode.
Some websites are able to detect running in incognito mode because some browser APIs are disabled there, but not in temporary containers
You can restart your browser without losing what's it your incognito windows.
So it stores full state when the application is closed, that's a long way off "incognito". Was it always like that?
I expressed myself poorly. In retrospect it sounds like the exact opposite of what I meant, in fact.

What I meant is if you open what you would otherwise open in an incognito window in a container instead, you can restart your browser without those tabs being closed and the respective state being lost.

i use this, it sounds like in a way inverted from the way you do -- i have containers for any site that i want to maintain persistence on, then default to a tmp container
I use this and it works well. You can also add a prefix to your temporary containers. I prefixed mine with “Mr. Meseeks #<Container Number”, which made it pretty hilarious if you also use the “kill tab after time” setting: Mr. Meseeks tabs closing in the background, completing their purpose.
for 1) do look into the temporary containers extension.
Cookie AutoDelete is great for custom site-specific cookie policies and is container-aware, see

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

thanks, i installed this. I couldn't find a way to set it to 'always delete everything from container x and never anything from container y' though.
The rules are container-specific, but you need to enable this feature first, it is off by default.

Settings -> Extension Options -> Enable Support for Container Tabs

The Mozilla VPN is a relabelled service by Mullvad VPN.
It has its own client application so it's a little more than simply relabelling a product. I find Mozilla client easier for less techy people so I guess both products complement themselve by targeting a different subset of the population.
You can apply a per container proxy, so if you run a proxy that goes through your vpn, you could do this with protonvpn. I do this with a ssh tunnel.
In regards to #1 - we have a feature (WIP right now) that adds the ability to delete data (cache, cookies and local storage) per container. Look for that in a future release.

https://github.com/mozilla/multi-account-containers/pull/249...

Oh wonderful, this will be a very welcome feature for me. :) thanks!
You can take care of #1 the way people here suggested, but I believe you can also do it backwards by having firefox delete ALL cookies at exit and whitelisting some domain's cookies. (Cookies sand Site data, check "Delete cookies and site data when Firefox is closed" and hit Manage Exceptions right next to it to whitelist some domains)

For #2 you do not need Firefox's VPN service. I am using it with wireguard and a socks5 proxy on the other end. I have a 'proxy' container configured but you can have more than one container with proxy as well. (In advanced proxy settings the syntax is socks://10.0.99.82:1080 )

Experience is still lacking compared to Chrome profiles. Chrome profiles are so much better UX wise than any other solution, especially the color coding of the window.
Firefox does profiles too.
But only with command line switches and relaunching, right?
Yes and from within the browser about:profiles

And you can edit the shortcut to ask you which profile you want to use when you start Firefox.

Never used command line for profiles, I'd just go type "about:profiles" > "Launch profile in new browser".

This opens a new window with that profile, but you can switch between each window at will.

The lack of discoverability of that "about:profiles" page is indeed a UX issue compared to chrome, but other that that it works pretty well.

For most use cases, I find the more lightweight multi-account-containers more useful though.

You can create .desktop files (or the equivalent in other OSs) for the profiles to open them like normal apps.
yup you log into a profile and then the containers and its profiles and settings are a child of that so you can use containers on different devices with same settings and containers
I'd argue it's far superior - no need to be switching windows constantly and setting the domain automatically loads that site in the correct context.
Multiple windows for me is a feature, not a bug.
Multiple windows for me is the Deal Breaker.

I want ONE window with all my tabs, in a vertical List (tree Style Tabs and/or Sideberry) which is another feature Chrome lacks completely, it implementation of Vertical Tabs is TERRIBLE

could care less about UX care about the data segmentation of which firefox is miles ahead
you can choose the color for container and it shows in ur tab
I've used these for over a year. Where the experience falls short is when using OAuth flows where either the requestor or provider is in a different container.

E.g. Slack (work) => Twitter (social media) => ~~broken~~ as the redirect doesn't go back to the (work) container.

I can't think of a fix because any there is would break the privacy of containers.

You can right click a link, and open it in the other container. It's clunky, but has worked for me so far.

The UX for default containers could really benefit from some kind of context-awareness, but I'm not sure what that would look like.

I'm thinking an intermediary tab that gives you a list of default containers (instead of only a single option or none at all) to choose from when opening a domain. Then, maybe, you could set a default choice based on the originating container. Or maybe a tree of sub-containers... This is where addon-defined UX makes sense.

The workaround I've used is to open slack.com in the Google container, etc. Not ideal, but it works.

In some cases though I do have to switch my default browser to Chrome, log in, then switch it back.

Love the feature and use it all the time. It would be great, if you could assign a home page to a container.
Would be cool if each container could generate a unique browser fingerprint. Right now they are sharing the same fingerprint, which isn't great for privacy.
I think this is what the Temporary Containers extension does? For me, it's a fundamental part of my browsing at this point, what I install immediately after installing an adblocker.

I feel resentful that the Temporary Containers extension isn't available on mobile Firefox. To me it would be as if adblocking extensions wouldn't be available. It's one thing of many that seems really different about mobile Firefox, to a point where the cynical part of me feels like mobile Firefox is being obsequious to advertisers or something for some reason in a way desktop is not.

would pay for this feature, does anyone know of another extension that does this to be used in conjunction?
A killer feature. Once I have tried Forefox's containers I am not going way...
I've been using distinct FF profiles to separate work browsing from personal browsing on the same machine. I give each profile a differently colored theme to visually separate the two and discourage accidentally using one profile for another's purpose.

Would multi-account containers be better for that workflow?

Succinctly yes, as this was what I was doing until recently.

I had about 6 or 7 Firefox profiles encompassing 2 of my businesses, clients, and some administration of my fiancée's companies she runs.

For each of my two businesses I had two separate profiles, one with personal accounts and a second I logged in with 'Admin' accounts for various services and infrastructure.

It was a little tedious, but it worked. However I would waste so much time tabbing through multiple Firefox windows working out what was the correct one for the job in hand.

Firefox Multi-Account containers got that down to two profiles, and I'd say I really only work 99% of the time in a single profile.

Simple Tab Groups is invaluable too to reduce the tab 'clutter' that comes from working out of a single profile/window.

Lastly as an added bonus, when I was comfortable with Multi-Account Containers, I successfully weened my fiancée off of Chrome and onto Firefox so she could flick between different accounts for those businesses she works with too.

This is so much more powerful than first party isolation in Chrome. Firefox is on the only browser with something like this. I love having multiple tabs open and logged into the same website with different accounts/cookies. I also use this in conjunction with Temporary Containers so every tab is a new container automatically. If I left-click a link it will navigate keeping the same container. If I control+click it will open the link in a new/separate container. Also I use another one called Container Proxy so some containers go out through different VPNs. As much as Mozilla is fucking up Firefox currently, this is the 1 thing no other browser does better.
But why is this REALLY "more powerful than first party isolation"? I don't need this feature every day, in case I do - just create separate profile and it's easy to run it right from toolbar. The only usecase I can remember: specific domains can be automatically opened in container - and that's a good feature to have, but not really a dealbreaker. Another difference: organization as a tab in the same window - not that really needed, just a different UI for not commonly used feature.
I use this with the Temporary Containers extension, so every tab is a new container, and a new session to the website I'm visiting. When I close the tab/container, all information about that site is lost. My browsing behavior - by default - is cookies live for as long as the container lives (and other cached elements). It makes me feel safer, browsing online, that I have to opt-in to remembering cookies and having them persist longer than the container. I can assign things over to the static containers like work-play-etc. For development I can have several tabs open with several independent sessions/logins going to the same website. When I tried to do this with Chrome it was 'clunky' to run separate Chrome profiles, which seem to be separate instances. I do remember an extension to do multiple in-the-same-browser sessions, but it was using a 3rd party service. I can have multiple sessions going in the same window in Firefox. As I understand, FPI prevents caching being used as a means to spy where you've been. My naive understanding is that containers encompass more than the cached elements FPI segregates, including things like fonts or localstorage. (I'm probably wrong) The only blindspot I see in Firefox is I wish preferences for extensions were per-container as well. I still use uMatrix, so if I've unblocked JS for a domain in 1 container, I don't want it unblocked for the same domain in an entirely separate container.

Also, for some sites where I do "Sign in with Google", I like being able to 'stitch together' those session cookies by opening sites in the "Google" container so i can just waltz right into the "other site". On my other containers, they don't have the session cookie for Google in the background so I'm good. I use this for work-related things with SSO. Instead of naming the "static containers" "Work, Play, etc", I just call them the SSO-provider, and I know if I move an existing container into that or open a new tab using that container it will have the login I need.

My default settings are pretty locked down. Umatrix blocks a lot in my new temporary containers, and then I gradually unblock things.

Wait, Firefox handles extension preferences globally? This is exactly what I've been wishing Chrome would do. I've spent a ton of time writing weird scripts and hacking Chrome to copy and sync various extension preferences from one profile to another.

Of course ideally I could specify specific extensions to work globally vs per profile.

(I'm perfectly fine having different profiles use different windows)

When I worked for an agency, I used this feature ALL the time. It had to be easy for me to switch between, for example, Trello boards of different clients or different Datadog accounts.

Even now, working at a single company, I use multi-account containers to keep tabs open for our different AWS and Datadog accounts.

Social media is dead. It was never social. If I had ads to sell, then I wouldn't be looking to spend the budget on deserts like Facebook and Twitter.
Perhaps a renaming would help this take off... Containers is overused in the dev world, and is rather ambiguous in the "outside."
Cargo containers from those big ships are well-known and people can assume that each container brings a set of homogeneous items. The word "container" pictures an isolated thing, which is what the add-on provides.
Couldn't live without this feature, I just wish I could have a ublock ruleset/whitelist per container.
Fifteen years ago I developed CookiePie [1]. You can see in the video opening two different gmail accounts in different tabs on the same window. This was a relatively successful Firefox extension to use separate and temporary cookie containers in different tabs. Since the Firefox API does include these capabilities, it was a pure hack, but it worked, just it was impossible to cope with every new upgrade of Firefox.

Briefly, the core of the hack was this:

(1) Firefox network hooks were not linked to UI tabs.

(2) So, I traverse all the object graph and find indirect links.

(3) I used those links to connect the network hooks with the UI, even when they conceptually were independent from the FF extension.

I sent the extension to the "Extend Firefox Prize" but didn't came with a single mention.

[1] https://www.youtube.com/watch?v=1EBkB-Yp-zM

Coolest feature is per container socks5 support so each container can send traffic through a different socks 5 server. Any VPN offering socks5 on their gateways should work. I'm using IVPN which expose socks5 on each of their WireGuard servers - there is demo on their blog - https://www.ivpn.net/blog/socks5-proxies-app-based-vpn-tunne...
With different profiles you have different settings -> completely independent connection settings, if you want. What's the difference here with Chromium profiles for example?
I think ff's containers are generally more powerful. Here's a random example: I live outside of the country I was born in, but I still have bank accounts and stuff there. These bank accounts freak out if I log in from my actual IP. Rather than needing to run a system-wide VPN every time I want to use one of those sites, I can set a rule that will automatically open them in a container (in the same window) with preset custom connection settings.
So sad that this feature (amongst many others) was present in Opera v12 (before they switched to Chromium). Still miss that browser, best UX ever.