I also want ephemeral containers so I could open a tab that forgets its cookies when I'm done. Think private browsing but without forgetting my history, requiring a new window, or being limited to one context at a time.
EDIT: Looks like there are already extensions doing that ! nice !
Can you send a link?
On firefox, "Self destructing cookies": https://addons.mozilla.org/en-US/firefox/addon/self-destruct...
You're welcome :)
Every time I use someone else's computer now, I'm horrified to see my settings from last time on random sites. You don't realize how much tracking is done until it's not the standard anymore. I even forgot to log out of places, so I've defaulted to opening private windows instead.
Anyway back in topic, SDC helps a lot but doesn't do everything OP wanted to do. I too would like to be able to open Facebook without wondering what other openings tabs might be using it, preventing SDC from removing the cookies. I'm really really excited Mozilla is doing this. SDC is a good start until it's out of nightly/beta though.
There are some browser extensions that to do this, but they're pretty clunky overall.
Mostly I see it actually working a lot like android's url-based intents, where there are things recognized as "apps" and actions directed at urls within that scope go to that 'app' to decide what to do with it, and things outside it go to a more traditional browser environment.
What they've implemented seems to be better than chrome's profiles, in that it's easier to create a new profile for a specific context (so I don't have to sort things into a "work" bucket and a "personal" bucket.) It will be interesting to see how the contexts interact with plugins.
«all» you have to do is go to ~/.mozilla/firefox/profile.ini and change it with:
Now Firefox will open a dialogue box at start-up asking you for the profile you want to use.
-P "<profile name>" Starts with a given profile name (profile name is case sensitive).
-no-remote Enables running multiple instances of the application with different profiles;  used with -P
case "$1" in
personal | work | banking | shopping)
firefox -no-remote -P "$1" ;;
*) echo "unknown arg: $1"; return 1; ;;
However, stymaar (https://news.ycombinator.com/item?id=11916985 )'s suggestion seemed to be specifically about avoiding the command line:
> I have an advice for you though, you don't need to open Firefox from a terminal if you want to be able to choose your profile at start-up.
I don't know, on Mac or Windows, how (although it would be nice) to wrap your script, or any other command-line executable, as an app that takes its arguments as parameters specified on double-click.
Basically, extension developers can "shim" their add-ons, which, as far as I understand it, tells Firefox that it has to handle things which are affected by the extension in a single-threaded way, again.
And because the world is a grim place, this doesn't just get you back to non-E10s performance, but is actually worse.
Eventually, add-on developers should properly port their extensions to E10s and then those performance problems will disappear, but at the moment they are still very frequent and when Mozilla rolls out E10s, they will also only default-enable it for users without extensions for this exact reason.
If you want to troubleshoot this, I would recommend looking at about:performance and www.arewee10syet.com.
You should probably check how performance is in a new profile first, though, just to make sure that you're not trying to replace extensions when it might be caused by something else.
"By clicking or navigating the site, you agree to allow our collection of information on and off Facebook through cookies."
I already have a separate chromium "person" set up for facebook; might give firefox another go when this gets released.
The only reasonable option, if one cares, is to use disconnect/ghostery/abp with the right lists, etc.
In case you are not aware: Every single web page that has a 'facebook like' button reports your surfing habits to Facebook, whether you have an account or not.
This is like saying, "By agreeing to take this person on a date one time, you're agreeing to take this person with you wherever you go from now until whenever."
In addition, I'd like the ability to fine tune which items are isolated versus shared. I think in many cases, but not all, I'd like to shift saved passwords and form data into the identity contexts and away from the shared context. Not having to manually manage credentials when using multiple distinct sessions of a single web service would be nice.
This can be unhelpful, though, if you need to have multiple tabs open on the same site.
I also wonder whether a seperate banking container makes a lot of sense when doing online payments, as in my country we get redirected to our bank to do payments. This might create confusion among non tech-savy users ("but this should be in my banking-container, I'll just switch. Why does the webshop give an error upon returning now?").
Overall a really cool feature though and one that might persuade me to give Firefox a try as daily driver again.
I think this is the actual solution to the problem that 'private browsing' was trying to fix when it first came out.
Besides, 11 FAQ and a long blog post: I'm not sure they narrowed down the most focussed feature that would provide the most value and be used by the most number of users.
Still sounds like a pain to manage though, compared to this new feature.
If there had been a safe way to secretly store that history, by having seperate identitie's in Firefox, (with password protection and crypto, etc...), that would've solved that case nicely.
And if you clear that secret, protected identitie's history, we'd have had 'Private Browsing', but also a ton more.
Which we're about to get now, it seems.
This is different. Cookies and storage are separated, but history, bookmarks, passwords etc. are shared 
- everything panopticlick uses (fonts list, plugin lists, timezone, agent, etc.)
- everything panopticlick doesn't use, but the bad guys do (aa font signatures, ...)
- plugin abuse - e.g., Flash 'cookies', Silverlight 'isolated storage', Java JNLP properties
- see EverCookie for more things that have been known to occur in the wild (and remember it is outdated). the article mentions cache is not shared, but e.g. HSTS pinning is. evercookie easily pierces through this system.
Since 2005 or so, I have had different users for different purposes; Not sure how well it works on Windows these days (it used to not work at all back in 2005) - but on Linux, it's just a "sux - otheruser" or "sudo -u otheruser" command away, and it is well isolated on the web side
 Full X11 isolation requires a lot more effort - but luckily it seems that recent browsers don't let websites abuse that
My post was not only a joke. This has serious potential to make multi-account tracking a nightmare... as it should, but not everything about that is good.
It's a really simple idea that can go a long way for digital identity hygiene. Can't wait to try it out.
 Screenshot of Qubes: https://www.qubes-os.org/attachment/wiki/QubesScreenshots/r2...
I hope they keep going into this direction
With Firefox containers I suppose I could drop my two Browser setup, but I won't, at least for now.
Four is not enough (personally, though I imagine it would be for most people) and remembering which identity is under "Work" and which is under "Shopping" is just an annoyance when none of my identities would be for "Work" or "Shopping". It would be faster and less annoying to sign out and sign in as another account. Being able to name my containers after my psuedonyms and have a container for each psuedonym would make it infinitely more useful and intuitive for me - rather than a mental burden not worth the hassle of using.
Although it is likely my social niche - I know more people with multiple personal or social accounts who will find this feature useful but have a terrible UX due to the container names.
"Hand me the long, blue screwdriver - by which I mean the short, red hammer." - terrible UX
I'll be providing concern this as feedback via email when I get home and have access to my personal email.
I think I'd love to be able to define which domains open in which contexts so if I click a link that happens to be to something I want in other context ...
But that got me thinking just how effective will this be? If someone sends me a link in fb and I click it. Even if it opens in a new context it seems like it's only a matter of time before all the links are changed to https://destsite.com/path/to/resource#fbtrackingid or something similar which then adds the cookie across contexts?
However, my personal vision is taking this one step further with an 'identity management' daemon running on your computer or a hardware token which acts a cryptographic agent on behalf of your identities. So firefox, chrome, or whatever application could request a credential for some service and your daemon would pop up and ask you which identity's credentials to use or if you'd like to make a new one (U2F or some other system).
What I have been doing is creating a separate Chrome application launcher for my different life contexts -- http://lifehacker.com/5611711/create-application-shortcuts-i... I have one for anonymous browsing, one for work, one for personal-real-name, and one for pseudonymous browsing. I renamed the application so I can launch by typing "WorkChrome" or "PersonalChrome" in spotlight search. Each Chrome app then runs with a separate profile, separate cookies, etc. I have a different icon and colored theme for each one, so that I never make a mistake with regards to which I am browsing in. I can have multiple open at the same time and tab switch between them.
I think this feature would have made tabgroups much more useful.
Now if only Firefox AddOns/Extensions would be able to properly access DBus, this would allow for a so much better Linux integration (storing passwords through org.freedesktop.Secret, opening URLs in the appropriate container from KDE Plasma sessions instead of random switches to another activity where a Firefox window is found, global media playback states/control for web video/audio as org.mpris.MediaPlayer2, powermanagement inhibitors through org.freedesktop.login1, etc)
People are also paranoid about online shopping sites changing prices based on tracking information. Here are two articles related to this: http://lifehacker.com/5973689/how-web-sites-vary-prices-base... and http://www.wisebread.com/6-ways-to-avoid-sneaky-online-price...
That said, no need to volunteer any more information than necessary to use online services.
If you haven't seen it, you should definitely check out https://panopticlick.eff.org/
I can't emphasize enough how much I've been waiting for this.
I've even tried pushing it via the dev-tools uservoice as a developer tool instead of a privacy tool, since you often need to test with multiple sessions at the same time. No reaction.
There is still the very real issue of fingerprinting across containers, which they point at towards the end of the article, but this might just be enough for me to drop Chrome completely and get my Firefox set up again the way I like it.
It currently has some delay when you open a new tab, and a few quirks here and there, but it's mostly working.
If you were going for something minimalistic and good for business/home usage, Chrome might be a better choice indeed. I can definitely see the advantages and I've installed it for my family back when it was substantially faster than Firefox (by now Chrome got a lot heavier and Firefox, uh, I guess they must have become a bit lighter but I don't know). I guess I should switch them back to Firefox again, but it might not be worth the learning curve.
Nothing changes really, ad revenue should already have been going down for years with how many ads we see every day. Almost everyone should automatically block them out mentally by now, and I think I recently heard this is starting to happen more and more now.
Having tabs from different contexts in the same window is confusing.
I prefer to use different devices entirely.
When need arises to have multiple logins to the same page I simply open new private window.
When submitting, I intentionally editorialized the title from something unclear out of mozilla's blog context ("Contextual Identities on the Web") to a more explicit title that speaks by itself ("Firefox 50 nightly new feature: Contextual Identities").
Isn't this considered valuable here?
- This guideline feels a wee bit sad, because editorializing can be valuable (a title might be crystal clear in context but nonsensical once pulled out of it).
- But I understand how we generally don't want it as it might lead to linkbaiting and misrepresenting the original title.
Had I not been subscribed to Mozilla's RSS feed, I personally would have skipped a "Contextual Identities on the Web (mozilla.org)" post on HN, because the vagueness would have made me mentally flag it as not time-worthwhile.
Contrarily, adding a few non-likbaitish words providing context (here, mentioning we're talking about a new feature in Firefox testable in Nightly, which is what my rename did), it becomes much more precise, less arbitrarily discard-able, thus interesting for certain people, including me.
But again, I understand the main reason the guidelines proscribe the practice: because it's a slippery slope to linkbait and incorrect reformulations.