Firefox: Always open site in Container Tab

Martin Brinkmann
Jun 4, 2017

Mozilla added a much requested feature to Firefox's Container Tabs experiment recently that enables you to always open sites in a specific container.

Container Tabs is an upcoming feature of the Firefox web browser that is available as a Test Pilot experiment, and in Firefox Nightly.

Mozilla launched the Container Tabs experiment a couple of months ago as a Test Pilot experiment.  We talked about the feature in 2016 before already when it was revealed for the first time.

Called Containers back then, it allowed participants to load websites in containers. A container is a closed environment which uses custom storage for some data to separate it from the main Firefox data storage and other containers.

This is useful for quite a few things, for instance to limit tracking, sign in to the same Web service at the same time in the same browser window, or to separate work from entertainment websites.

Firefox: Always open site in Container Tab

firefox always open container tab

In the closing words under the original article here on Ghacks, I mentioned that I'd like to see Mozilla add features to Container Tabs that I think would improve the feature significantly.

Among the features was a request to restrict sites to certain containers. This made sense in my opinion, as it would allow you to load bank websites in the security container, work related sites and services in the work container, and so on.

Mozilla has added the functionality to the latest version of the Container Tabs experiment. Note that this feature has not landed yet in the Firefox Nightly implementation of Containers.

A small informational panel is opened when you click on the Container Tabs icon in the Firefox toolbar after installation or update of the add-on in the browser.

It highlights that the "always open sites in the containers you want" option is now available. To use it, you right-click inside a container tab to assign it to the loaded container.

always open in this container

You may also right-click on the Container Tabs icon in the Firefox toolbar to check the option as well.

A prompt is loaded next time you load the site in Firefox. In fact, this prompt is loaded each time you open the site, unless you check the "remember my decision for this site" option.

container tabs prompt

If you check the box, the prompt is not displayed anymore. You can disable the loading of a site in a container tab by right-clicking either on the site or on the icon while the site is loaded in the active tab.


Mozilla continues its work on the upcoming Container Tabs feature. While it is still possible that the feature won't land in Firefox, it seems very likely that it will land eventually.

My hope is that Mozilla will address my other feature requests, especially the option to clear data only in a single container tab, as well in future updates. (via Sören Hentzschel)

Now You: What is your take on the improvement and Container Tabs in general?

Firefox: Always open site in Container Tab
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Firefox: Always open site in Container Tab
Mozilla added a much requested feature to Firefox's Container Tabs experiment recently that enables you to always open sites in a specified tab.
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  1. kelly said on November 17, 2021 at 2:06 am

    please why does it always ask me to open in a current container or work container instead of just open in current container ?

  2. BoulderCO said on August 4, 2017 at 5:00 pm

    Does Chrome have a similar or comparable extension by chance?

  3. XenoSilvano said on June 6, 2017 at 7:44 pm

    I thought electrolysis brought tabbed sandboxing

  4. pd said on June 5, 2017 at 5:01 pm

    Here comes something I never thought I’d say. At least, not often.

    “Containers” is a very generic, almost meaningless term. For the sake of the average user, or even us techies with fond childhood memories, what’s wrong with taking the security concept term “sandbox” or similar, and using it here? Where are those logical, sensible marketing types when you need them? :) LOL

    1. TMX said on June 5, 2017 at 8:21 pm

      Agree with you.

      “Sandbox” is better terminology.

    2. Pants said on June 5, 2017 at 6:45 pm

      Probably because using “sandbox” would cause confusion. This is not about separating running processes for security, but separating data for privacy. A “container” is very apt name IMO.

  5. Maelish said on June 5, 2017 at 3:16 pm

    Hopefully they will add better sandbox features in the future. It’s an interesting idea.

    Btw Martin, you’ve done a better job of explaining containers than Mozilla.

  6. Rick A. said on June 5, 2017 at 2:47 am

    Martin or Soren, or someone else can you please answer, is it possible to clear the Container data for a Single container or at least clear the data of all containers, either using the Test Pilot add-on or without the Test Pilot add-on by toggling the preference privacy.userContext.enabled ? How would one clear the data? For instance if i toggle the preference to false and re-enable it will the container data be cleared? And what about using the Test Pilot add-on?

    Thank you in advance for any help.

    1. Rick A. said on June 5, 2017 at 5:10 pm

      @The dude – You must be a Google Fanboy to make a comment like that.

    2. Pants said on June 5, 2017 at 11:25 am

      Containers are still experimental, but can be run in stable (just not all features). Regardless, they currently use all the things “normal” windows do (as opposed to Private Browsing mode). So, if you clear cache, it clears container cache as well – if you clear cookies, it clears container cookies as well, and so on.

      See this ticket:
      “This bug is to make sure “Clear History” will apply for all containers for v1″
      Clear History (Ctrl-Shift-Del) allows specific items to clear, eg cookies, various histories etc

      See this ticket: [Unassigned]
      “We should allow users to clear history only within certain contexts. This includes both the “Clear recent history…” Menu UI and the Privacy Preferences UI under “Clear History When Firefox Closes”. It can be exposed as a series of checkboxes so multiple contexts can be cleared at the same time.”

      1. Rick A. said on June 6, 2017 at 3:51 pm

        @Pants – Yeah, i know about that add-on not being a web extension but i saves a few clicks compared to how i used to do it which is having about:preferences#privacy as a pinned tab-(and still is pinned) and also doing it with Ctrl+Shift+Del. Being a mouse user it’s easier to just hover the mouse over and click the Clear Console button. But, i’ve actually been considering disabling it and giving Cookie AutoDelete another try or just doing it the old way mainly because i want to be all Web Extensions and have Multi Process, which i know i can force it but have chose not to in case i have any issues by doing it which i’m sure you can tell me if i will have any issues and i hope you do tell me.

        i’m also wondering if multi-process will enable by having all non web extensions disabled or if i have to uninstall them and if i don’t have to uninstall them and am on multi-process, if i enable an old add-on does Firefox tell me to restart Firefox and it re-opens with multi-process disabled? And disabling that old add-on and restarting Firefox i’ll be back on multi-process Firefox? i have searched and couldn’t find a thorough answer for this.

        As for dom storage i use a bookmarklet from to view it and also but it doesn’t work the way i want it to, which i just asked the creator of the add-on about Also i just set to false to see if i have any problems with websites i visit which so far i haven’t.

        As for containers i think i’ll try it by enabling it in about:config and going from there, but i don’t know if it will work for G-mail/YouTube, which is the only reason i have a G-mail for, i checked the e-mails for YouTube and when i click them it opens a new tab on YouTube for that video, i’m pretty sure i can set g-mail and YouTube to use the same container or i might have to use the Test Pilot add-on for that.

        Thank you for your past responses and answers Pants and thank you in advance if you answer my questions in the post or anybody else that answers them, it will be appreciated.

      2. Pants said on June 5, 2017 at 9:45 pm

        Sorry, forgot to answer the question. The test pilot obviously allows more experimental features, earlier adoption (by the looks of things up to two or more releases early). It also fixes some bugs which you won’t get if you just used it without the test pilot etc (eg missing icons, color issues etc if using full themes etc). And the telemetry would help the end product – of course you can always comment in the github site and give feedback/reports/suggestions – . I wouldn’t worry about the telemetry as a downside.

        If you’re into containers, quite frankly, the “always open site in container” alone should be enough to get the test pilot already, IMO. Personally, I’m going to wait, as I feel I already control almost everything in my default one and only “container”, normal FF.

      3. Pants said on June 5, 2017 at 9:37 pm

        @Rick A – dump that extension is my advice (its legacy and will soon be obsolete). You can achieve all of that (except local dom storage i think, more on that in a sec) but using the built in Clear History (no button I’m afraid)

        If you check out the revamped section 2800 in the ghacks user.js, you can preset the time range to clear on startup (it remembers the last setting used), and preset the seven items to clear. Section 2804 – shows 9 items, the dialog shows 7. 1 item is not used (downloads) as it it tied to one of the other ones (history), and passwords is not listed.

        It’s not hard to go Ctrl-Shift-Del and hit enter (yup, the focus is already on OK) – *almost* as good as a button. I used to use a button as well, but ditched it a year ago. Maybe when 57 lands and more dev port over, something magic will appear.

        As for local dom storage, I haven’t really found the need, as I block it with my cookie addon – cookie controller blocks all cookies except for about a dozen I allow. This also blocks dom storage. And those few sites I allow cookies are always blocked elsewhere via XSS. Quite a few cookie addons seem to deal with dom storage – no idea why. I’m not an expert on it.

        Long term, I’m hoping FPI (first party isolate) will control all of this, so it doesn’t matter if you allow dom storage or cookies or even 3rd party (to an extent). This should be ready to go in 55, definitely by 57 (its been around since 51 but needed a lot more work)

      4. Rick A. said on June 5, 2017 at 6:45 pm

        @Pants – Thanks Pants. i use an add-on Clear Console that puts a button on my toolbar that i use to clear cookies every time i leave a website, so it wouldn’t be useful to me unless i sign into multiple websites at the same time and when i’m done just clear everything and start over. One more question Pants, is there any reason why i should use the Test Pilot add-on or by enabling privacy.userContext.enabled over the other? i know some telemetry comes with the add-on, but any other advantages for either one ?

      5. The dude said on June 5, 2017 at 3:37 pm

        Dude, Mozilla is the NSA, man. I’m telling you… the government, man.. I don’t trust them. Duuude,

  7. Peter said on June 4, 2017 at 11:40 pm

    Brave browser has an equivalent called session tabs. It’s pretty handy and a logical improvement for any tabbed browser.

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