Tab Data for Firefox highlights memory usage of each open tab

Martin Brinkmann
Feb 20, 2015

We all know that some websites require more memory than others. If you open a simple static page like our IP checker and compare it to Facebook or any other large site with lots of contents then you will notice that static sites may require less than 1 Megabyte of memory while sites such as Facebook 40 or more Megabyte.

Firefox, unlike Chrome, does not offer a Task Manager that you can use to look up how much memory individual tabs require.

While there is an add-on available that reveals the memory usage of add-ons installed in the browser, no native option or add-on has been available up until now that does the same for tabs.

The Firefox add-on Tab Data has been designed for that purpose. The add-on, once installed, displays the memory usage of each site open in the browser.

firefox tab memory usage

The information is displayed on the left side of each tab. There you find listed how much memory it is using at that point in time.

Tip: The collection interval is set to once per second which may slow down the browser considerable. You may want to modify the interval in the options so that memory data is only collected every 30 seconds or so.

The information are updated automatically based on a memory data collection interval that you can modify in the add-on's options.

You will notice that memory usage fluctuates depending on whether the tab is active or not, and that it may drop as well.

The memory usage is only displayed for sites loaded in tabs. If you have configured Firefox to only load selected tabs on start you will only get memory information for these tabs and no other.

The add-on places an icon in the main toolbar that reveals basic information about tab usage in the browsing session. In particular, it reveals how many tabs are open at that point in time, how many tabs were opened in the session up to this point, and how many tabs were opened in total since the installation of the add-on.

You can remove the icon easily from the toolbar if you are not interested in the information.

Probably the biggest issue that I have with the extension is that it displays the information on the left side of the tab title. This means that it may reduce the visibility of page titles in the browser. The author should consider creating a local page listing all tabs and their memory usage.

For now, it seems practicable to use the add-on for a while to find out about sites that use a lot of memory and disable it completely or the memory usage tracking in particular.

All in all though this is a great add-on that reveals important information about websites that you visit in the Firefox web browser.

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Author Rating
5 based on 1 votes
Software Name
Tab Data
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  1. Joe said on April 18, 2015 at 4:18 pm

    Tab Data freezes my Firefox, so I use instead. Very similar but lighter in my opinion.

  2. bobbyrne01 said on March 7, 2015 at 7:03 pm

    For anyone interested I’ve just released v0.4.1, which has a new graph feature showing top 5 tab memory consumers:

  3. bobbyrne01 said on February 24, 2015 at 1:32 pm

    For anyone interested, v0.3.0 is now released on AMO.
    Which allows users to free memory within Firefox with click of a button and cleans tab titles if settings are disabled.

    1. PJ said on February 25, 2015 at 4:37 pm

      @bobbyrne01 — I installed Tab Data v 0.3.1 from AMO.

      1) At about:Addons > Tab Data > Options UI, there is a caption called Show memory usage in tab titles with default value = 0, but no indication of what “0” stands for.

      I initially thought 0 means disabled, ie. don’t show memory usage in tab titles. After some fiddling, I realized that for this case:
      • 0 = Prepend • 1 = Append • 2 or [Blank] or [Any Other Integer] = Disable

      Since it is counter-intuitive that 0 does not actually mean disabled, the aforementioned caption can perhaps be improved to provide some clues of accepted values, or else reconfigured such that:
      • 1 = Prepend • 2 = Append • 0 = Disable

      Or better still, since the check-box is already being used for one other existing caption in the Options UI, is it possible to use check-boxes instead ?
      ☑ Prepend ☐ Append ☐ Disable

      2) Regarding locaton & timing of the memory usage indicator, how about providing an extra option ?
      ☐ Prepend for first X seconds (ie. after each memory collection)

      For instance, if user specifies 30 secs interval between memory data collections, specifying X = 10 will prepend the memory indicator for the first 10 seconds, & thereafter disappear from tab titles.

      3) For newly-opened links, new tabs & reloaded tabs, is it possible for the memory usage indicator to appear immediately, instead of waiting for the next collective memory data collection ? After that, the indicator timing can sync with the rest according to user-specified interval.

      1. PJ said on February 27, 2015 at 7:13 pm

        @bobbyrne01 — I’d just manually upgraded my Tab Data from v 0.3.4 to 0.3.6 at AMO. Thanks for the tweaks.

        VERIFIED FIXED #3: After Prepend ↔ Append switch, memory indicators on tabs no longer disappear & then take random time to reappear.

        It appears that certain scheduled functions are still not being reset within the expected & predictable time range, as follows …

        Output-format at Panel UI > Message Usage takes random time to change, after JSON ↔ Plain switch:
        4a) Switch done at Panel UI > Settings ⇒ OK, no apparent lag in output-format change;
        4b) Switch done at Addons > Options UI ⇒ Random time-lag before output-format changes.

        5) Tick or untick “Show Url on memory usage panel”:
        Random time-lag (4–53 secs) for format change, regardless of whether it is done at Addons > Options UI or at Panel UI > Settings.

        6) For newly-opened tabs, or different URL newly-loaded on same tab:
        Random time-lag (4–61 secs) before new tab entries get listed, & existing entries get updated with the new page title at Panel UI > Memory Usage.

        7) After 1 or more tabs are closed:
        Random time lag for corresponding entries to disappear from Panel UI > Memory Usage.

        Outcome of above: The ‘Memory Usage’ list at Panel UI can be quite confusing because closed tabs & defunct URLs are still listed for XX secs, while new tabs & newly-loaded URLs on existing tabs are not captured until possibly after XX secs. It’s rather like trying to figure out if something is a zombie (lingering around), or a ghost (extant but can’t be seen).

      2. bobbyrne01 said on February 27, 2015 at 4:01 pm

        @PJ, v0.3.6 uploaded to AMO which fixes #3 and #4 :)

      3. bobbyrne01 said on February 27, 2015 at 1:23 am

        @PJ great input, thank you!

        #3 & #4, totally agree, this is caused by not resetting the scheduled functions when those preferences are changed. ill fix those in v0.4.0

      4. PJ said on February 26, 2015 at 6:57 pm

        @bobbyrne01 — Firefox didn’t push the latest version of Tab Data to me, so I manually installed v 0.3.4 from AMO on top of v 0.3.1.

        Thanks for the new dropdown menu at about:Addons > Tab Data > Options UI. Looks good ! No confusion now, esp. for new users who may not immediately spot where the Tab Data icon is on the Firefox toolbar, or when Firefox hides the icon within the ≡ menu. Looking forward to new features & improved functions in v 0.4.0. Meanwhile …

        (3) Right now, when user switches between Prepend & Append, all existing memory indicators disappear from the tabs, & one has to wait for a seemingly random amount of time (see below, tested consecutively) to ascertain if the option switch worked or not. Possible to not make the memory indicator disappear, unless user chooses Disable ?

        Memory Data Collection Interval vs. Sampling of Memory Indicator Lag after Prepend↔Append Switch:-
        • Interval: 10 secs ⇒ Lag: 3, 9, 10, 32, 58, 62 secs, etc.
        • Interval: 60 secs ⇒ Lag: 2, 6, 48, 49, 53, 61 secs, etc.

        (4) Likewise, when user switches between Plain & JSON, there is a random time-lag before the output-format changes at Panel UI > Memory Usage.

      5. bobbyrne01 said on February 26, 2015 at 12:43 pm

        Regarding #1, I’ve uploaded v0.3.2 to Mozilla which uses a dropdown menu instead of a number to change setting, should be easier for users.

      6. bobbyrne01 said on February 25, 2015 at 8:13 pm

        Hey PJ,
        Thanks for your feedback! See responses below ..

        #1, The dropdown menu you see on the Panel UI, I plan on adding that to the ‘about:addons > Tab Data > Options UI’ UI too. Which should prevent any confusion :)

        #2 Yeah, I like that idea .. will add it into v0.4.0

        #3 Sure, I will add a feature so that ~2 seconds after opening/reloading a tab, the stats are updated

  4. Mystique said on February 22, 2015 at 9:02 am

    I guess the colour scheme could be used as apposed to the actual numbers being displayed and the more detailed data can be displayed within a separate page.

    Perhaps the issue of active tabs can be implemented when Firefox becomes multi process and handles tabs separately and you could keep that idea in the pipeline. ;-)

    I honestly think its a great idea as I know some sites are for example flash intensive and some items may not be completely necessary and most likely the cause of the issue therefore I could block it with the knowledge I have acquired using your addon.

    Haha I was so tired when I wrote the comment that the actual correct spelling of “Threshold” had escaped me lol.

    Thanks again for the addon and the reply.

    1. bobbyrne01 said on February 22, 2015 at 3:08 pm

      Sure, I’ll keep the active tabs querying in mind.
      I’ve released v0.2.6 on Mozilla which displays the memory stats in the Panel which shows when you click on the icon. You can also remove the memory stats from tab titles, which should take up less screen space for you.
      Haha I knew what you meant, and your very welcome!

  5. Mystique said on February 21, 2015 at 12:45 pm

    Perhaps another option would be to have default fresh holds and when the fresh holds are reached the tab can become red, one could also go with the traditional traffic light colour scheme red, yellow, green with each colour being optional via tick box as I imagine no one would want all their tabs being highlighted green all the time.

    Another way of cutting down CPU usage would be to only have it work with active tabs honoring the system in place which suspends background tabs.

    Overall I do agree with the additional page option and disagree with those that feel that this is merely a developers tool. As a user I would love to know how much a tab is consuming as I may be able to isolate a problem with said site or perhaps it could indicate an issue with a script being used within greasemonkey. It would also help me to modify my behaviour by not leaving heavy tabs open constantly leeching resources unless I absolutely need to.

    1. bobbyrne01 said on February 21, 2015 at 1:29 pm

      Hey Mystique, appreciate your input! I love the idea of the traffic light system, if a tab’s memory goes beyond a threshold its color will change .. I will add this functionality very shortly :)

      About only working on active tabs, I’m not sure if thats possible because when you request memory stats within Firefox, all data is returned by default .. you cannot limit which tabs you’d like to query, to my knowledge.

      And thank you, I totally agree that this is an addon not only for developers but for all users interested in memory consumption.

  6. Guest said on February 21, 2015 at 10:27 am

    Looks like a great addon, though it does seem to take up a lot of space at the beginning of each tab. Perhaps an option to only show the whole number alone would help.

    11.2 MB:

    See the difference? It wouldn’t be confusing, because only those who choose this option would be able to view it.

    1. bobbyrne01 said on February 21, 2015 at 1:23 pm

      Hey, I see how this would save valuable tab space but what if a tab was displaying 100. How does the user know if this is 100 KB or 100 MB? Knowing the difference between these values is a necessity in my opinion.

      1. Guest said on February 21, 2015 at 10:00 pm

        0.xx for KB as Martin said.

        @Boris: now that I have it, I always want to use it. Being able to toggle it on/off wouldn’t be as useful to me as simply shortening it would.

        Also: would be nice to have minimum view option. For instance any tab using less than 10 MB (variable), don’t show a value, only show tab values over.

      2. Boris said on February 21, 2015 at 9:24 pm

        Even simpler. Turn it off and on from button or right click tab menu. Use it only when you want it.

      3. Martin Brinkmann said on February 21, 2015 at 1:31 pm

        How about displaying 100KB as 0.1 then?

  7. Boris said on February 20, 2015 at 10:37 pm

    I saw Ram use numbers on Tabs today and immediately thought: “Did they update Firefox today or something?”. Finally, I did a search and came to this article.

    I do not really need to know how much RAM each page uses. I know for example Amazon probably uses 5 times more RAM as usual page. And I will still use Amazon.

    With 4 pages opened(No Flash) (150Mb Ram combined), my Firefox was already approaching 1GB Ram. Here lies a problem. I use a lot of extensions. I know high Ram usage is from leaking extensions. Regrettably, there is no way easily check which extensions (except for AdBlockPlus) are memory hogs/leakers. If anybody creates extension to reliably check extensions for memory load, that would be a great day.

    1. bobbyrne01 said on February 21, 2015 at 12:47 am

      Hey Boris, as Roy pointed out the ‘about:addons-memory’ addon probably is easiest way to determine how much memory each addon is using.
      If that is not enough, combined with ‘Tab Data’ addon, then you should probably look at ‘about:memory’ in your address bar .. this will detail all memory in use by Firefox.

    2. Roy said on February 20, 2015 at 10:59 pm
      1. Boris said on February 20, 2015 at 11:59 pm

        This one does not tell the whole story. It shows total memory consumption around 200Mb, while real Firefox memory consumption right now is 1.4Gb.

        When you divide total from the table by actual percentage, you can get exactly Ram amount consumed by Firefox. But how do I know what other 86% of Ram allocated too.

        It is like studding universe but without astronomer’s skills. You know visual mass of universe and you know actual mass of universe. Where do you look for the dark matter.

  8. Tom Hawack said on February 20, 2015 at 5:06 pm

    Data collectors may be pertinent for developers but for the user nothing more than interesting if the user understands what the collected data means. What will a RAM per tab knowledge bring to the user? Heavy site? Tell me one user who will stop accessing a site because it uses a lot of his browser’s RAM. This add-on is a gadget which consumes CPU cycles as noted in the article in proportion of the collection interval… the typical add-on I avoid, brings me nothing. But may be worth it for others in which case I’d be happy to know why, besides curiosity of course.

    1. bobbyrne01 said on February 20, 2015 at 7:31 pm

      Hey Tom
      Being a developer myself I love to understand software and the impact it has on my machine, whether its a server, desktop app or web site.

      The addon helps users understand what tab may be misbehaving in their browser so they can possibly close it, as Martin suggested.
      And for web-developers it could help identify memory leaks in their own code.

      If you don’t like the memory stats about your tabs, you can disable them via the preference :) then you will just have open tab counts.

      1. bobbyrne01 said on March 5, 2015 at 3:25 pm

        @PJ from what i can tell the EmptyWorkingSet is a Windows specific api, I’d like to avoid making calls to platform functions until the addon reaches a more mature stage.

      2. PJ said on February 26, 2015 at 7:09 pm

        @bobbyrne01 — Besides Cycle Collector, is it possible to also make Tab Data’s ‘Garbage Collection’ function invoke EmptyWorkingSet API ?

        Would that conflict with Firemin, which automatically runs EmptyWorkingSet API call a few times per second in the background ?

      3. bobbyrne01 said on February 25, 2015 at 8:18 pm

        @PJ, nice comparison between ‘Tab Data’s memory clean up and ‘CleanMem’.
        It is likely that ‘CleanMem’ is invoking cycle collector aswell as garbage collector, which would help release more memory. I hope to add calls to cycle collector into ‘Tab Data’ soon too.

      4. PJ said on February 25, 2015 at 5:21 pm

        @Tom Hawack — The ‘Tab Data’ add-on is not just about showing memory usage statistics on open tabs.

        At ‘Tab Data”s Panel UI, there is an option to Perform Garbage Collection. I was wondering if this function can help manage (high) global memory use by Firefox, & release no-longer-needed but otherwise Firefox-locked memory for other uses.

        With Firemin closed, internet disconnected & all Firefox tabs closed except for one (13.5 MB), below is Firefox’s Global Memory Usage after 2 consecutive runs of each of the following:-

        • Tab Data’s Garbage Collection: 300,000 K → 281,000 K
        [can’t be reduced any further, even when run more than twice consecutively]

        • CleanMem: 285,000 K → 1,700 K

        Where I am concerned, whether to keep the ‘Tab Data’ add-on enabled (or even uninstall it) depends on how much memory it uses, in comparison to how much it might help release.

      5. Tom Hawack said on February 20, 2015 at 8:10 pm

        Should I use this add-on it certainly wouldn’t be for the opened tabs counter : I never have that many tabs opened and when I do it’s accessing the right one that matters to me rather than how many there are…

        I conceive perfectly well that this add-on aims to resolve a questioning not handled by any other add-on, it has been conceived, thought, elaborated and coded. That in itself is worthy. Worthy as well, that contrarily to what I expressed above incorrectly, even if a work is unused practically speaking it remains a brain’s labor and setting things may always appear to be valuable later …

        For the time being, I don’t care how many opened tabs are on the browser’s floor and the RAM they use is the last of my concern. I am concerned buy the browser’s global usage of RAM & CPU but that’s about all.

        But : great if it can be useful for as many as possible.

    2. Martin Brinkmann said on February 20, 2015 at 5:10 pm

      Tom, it could change when you access specific sites. Say there is one that uses hundreds of Megabyte of RAM. If you run Firefox on a low RAM system, you may want to open that site on its own without other tabs open or maybe even in another browser.

      1. Tom Hawack said on February 20, 2015 at 5:39 pm

        Yeah… maybe :) I have no doubt the developer made his best to conceive an add-on running fine. Generally speaking it’s the concept which carries a project that may be pertinent or not. Nevertheless I understand your point, but it’s maybe the only one :)

        When you have a look at AMO (Firefox add-ons’ pages) you can spot several add-ons which seem to have been aimed at a developer’s exercise : can we, can I do this ? Forgetting that like business an add-on must have a plan. Most add-ons do have that plan, I mean are built on the basis of a valid concept but remains a low percentage of extensions which serve… nothing, unless theory, like that branch of physics which calls the scientist’s deep thoughts but which wil never be useful for anyone until it proposes something answering a need…. Never mind… :)

  9. bobbyrne01 said on February 20, 2015 at 4:25 pm

    Thanks for the review! I’ll look into creating the local page you suggested :)

    1. Martin Brinkmann said on February 20, 2015 at 4:49 pm

      Bobby thanks for joining the conversation. Looking forward to that implementation as it should improve the visibility of the data by a lot.

      1. bobbyrne01 said on February 22, 2015 at 3:09 pm

        @Ken, I can’t seem to reply to you directly in this thread, no reply button beside your name.
        Anyway, the tooltip is a great idea! I’ll look into adding that feature too.

      2. Ken Saunders said on February 21, 2015 at 2:24 pm

        I haven’t tried the add-on yet but I will be.
        I love the concept.

        “I’m going to add 2 new preferences ..
        1. Show memory usage in tab titles?
        2. Show memory usage in separate tab?”

        Your #2 there is a good one, but how about displaying the memory usage in a tooltip (upon hovering over the tab) instead of in the tab title so nothing in the tab title is lost and you wouldn’t have to shorten or abbreviate anything? I’m not sure how that might work since the page title shows in the tooltip, but I’m pretty sure that I’ve seen add-ons (or at least one) add info to tab tooltips.

        Others (perhaps not as helpful)

      3. bobbyrne01 said on February 20, 2015 at 7:10 pm

        No problem! Yeah agreed, I’m going to add 2 new preferences ..
        1. Show memory usage in tab titles?
        2. Show memory usage in separate tab?

        that way you can choose where data will be displayed in browser.

  10. shady4ever said on February 20, 2015 at 4:03 pm

    “The author should consider creating a local page listing all tabs and their memory usage.”

    yes yes yes please !!!!!!

    We need either a dialogue box (similar to chrome) or a new tab listing all the details and an option to close/disable desired tab/s.

    PS – its slowing down my browser (low end system) so not suitable for all time use :(

    1. bobbyrne01 said on February 20, 2015 at 7:15 pm

      Hey @shady4ever
      Yeah, I’m looking into adding a separate tab which displays the data.
      Also in version 0.2.4 I set the default collection times to be 10 seconds so should keep browser more usable .. of coarse the user preference exists for you to adjust too.

      1. bobbyrne01 said on February 22, 2015 at 9:31 pm

        Really appreciate your input shady4ever! And glad your making use of the feature :)

        Responses to your feedback:
        1. Yeah, I’ll switch them for v0.3.0 .. memory stats are gonna be more popular than tab counts.
        2. I’ll include url in description for v0.3.0 too. Still looking into how to organise the data so its as clean as possible :)
        3. Mozilla’s addon site seems to be having trouble, cant upload v0.2.7 or new images .. ill try again soon.
        4. Good idea on the reddit post ;)

        About your ‘ps’ request, I think addon’s memory usage is outside the scope of this addon to be honest. Could using ‘Tab Data’ and ‘about:addons-memory’ be enough? If not, your welcome to create any bugs or enhancement requests here:

      2. shady4ever said on February 22, 2015 at 7:59 pm

        Hi bobby, just checked the new 0.2.6 version. Its getting better and better :)

        Some Feedback (not pressuring you to do overtime ) –

        1. May be “memory usage” can be first tab in the panel and then tab “counts” second tab.
        2. Memory Usage description is a bit messy. See here – May be you can include URL in the description too.
        3. Time to update screenshots and ‘About this Add-on’ on Mozilla’s extenstion page :)
        4. Make a new thread on with a title something like – “After receiving feedback I made some changes in Add-on ‘Tab Data’. It displays the memory usage of each open tab.” Maybe some people might wanna take second look at it.


        PS – just curious, Is it possible to display memory usage of both tabs and extenstions at the same place same time???

      3. shady4ever said on February 20, 2015 at 8:56 pm

        Hi Bobby, nice to see you engaging in the conversation.
        It was the absence of Task Manager that i missed most when i switched to Firefox 2 years ago and unfortunately there was no user friendly extension for this till now. So, your add-on is pretty useful for my low end system.

        I have already set the collection time to 30 sec. Will look forward to further updates. Thanks in advance.

  11. iarno said on February 20, 2015 at 3:55 pm

    May I ask what theme you use in the Firefox screenshot pictured here ?

    1. Martin Brinkmann said on February 20, 2015 at 4:10 pm

      Default theme optimized with Classic Theme Restorer add-on only.

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