How many tabs do people use? (Now with real data!)

April 13, 2009 ⋅ hci, research, browser ⋅ 21 Comments »

For the past few months, I’ve been knee-deep in data from the tabbed browsing study that I conducted late last year. Now that I’m finishing up my thesis, I figured it’s about time that I share some of my findings. In this post, I’ll talk about one of the quantitative questions I was trying to answer in my study: how many tabs do people use?

Measures

The first thing we need to do is to be a bit more precise with the question. What does it mean to “use” multiple tabs or windows, and how should it be measured? There are few possible answers.

We could simply count the number of tabs that a person creates. One problem with that is that when Firefox starts up, at least one tab is created (and possibly more, if it is restoring a session), so someone who opens and closes their browser frequently would have a high number of tab creation events. To eliminate this effect, we only count tabs that are created after browser startup. We also ignore the first tab that is created in any window.

Another thing that’s interesting to measure is the number of concurrent tabs or windows that a person typically has open. For example, two people might create a similar number of tabs, but one of them might have an email client, an RSS reader, and another tab playing music open at all times. It seems reasonable to say that this person uses tabs more heavily than the other person. We decided to measure the number of windows and tabs that were open whenever a navigation event occurred. For consistency, we ignored all navigation events caused by Firefox’s session restore feature when calculating this measure, although it didn’t have a very significant effect overall.

A third measure of tab usage that might be interesting to look at is the number of tab switches that a person performs, but I’ll address that in a later post. For now, we’ll concentrate on how many tabs.

Study Details

First, I guess I should mention a little bit about how the study was conducted. Here was the recruitment email we sent out to family, friends, and colleagues:

We are seeking participants (at least 18 years old) for a research study exploring how people use web browsers.

If you use Mozilla Firefox for several hours a day, and often use multiple tabs or windows, then you are a candidate for the study. If you choose to participate, you’ll install a Firefox extension that will log various actions, e.g. clicking on a link, visiting a bookmark, opening a new tab, and clicking the back button. Don’t worry, the names and addresses of the web sites that you visit will NOT be revealed to researchers.

The study will last for two weeks. During this time, you’ll take part in five short interviews (approx. 30 minutes each) that will be arranged at your convenience. In addition, you’ll be asked to record some brief notes several times during the course of each day (again, at your convenience) and to email your log file to the researchers at the end of the day. Participating in the study will take about 4-5 hours in total over the two week period.

We also put posters up with similar wording across the University of Toronto campus. 21 people completed the study, and 1 person started it but dropped out early.

Unlike many other studies like this that have been done, our study participants had a variety of ages, professions, and technical skill levels. One participant was younger than 20, 14 were between the ages of 20 and 29, four were 30-39, and two were 50-59. Only 6 participants came from a computer science or engineering background, while others had studied education, environmental science, business, and psychology. Six of the participants were full-time students (either undergraduate or graduate), and 15 were working in some kind of office environment where they spent most of their time on the computer.

Results

Tab Creation

First lets take a look at the tab creation rate. Now, keep in mind that these are only tabs that are created after browser startup, and the first tab in any window is not counted. On the X axis is the “tab creation rate”: the ratio of tabs created to navigation actions. (A navigation action is anything that changes the URL of the page, even if it doesn’t result in a top-level page load.) The height of the bars represents the number of participants with a given tab creation ratio.

Histogram of tab creation rate

Interesting…we’ve got a very clear bi-modal distribution. More than half of our participants (13/21) are clustered around the 0.04 mark. In other words, these people create about 4 tabs for every 100 navigation actions. The rest of the participants are loosely centered around 0.14, meaning that they create about 3 times as many tabs as the other people. In fact, we have two participants who are even higher, creating (respectively) 17 and 22 tabs per 100 navigation actions.

Unsurprisingly, the four highest tab creation rates belong to the four participants with Computer Science and/or programming backgrounds. The other four participants in the high part of the distribution are not your typical “techie” types: one is trained as a civil engineer, and the others have backgrounds in communications, humanities, and marketing.

Concurrent Tabs

Another interesting thing to look at is the number of tabs that people tend to have open at any given time. Again, we used navigation actions as our increment of measurement. On the X axis is the number of tabs open when a navigation action occurs, and the height of the bars it the total number of navigation actions that occurred with the that number of tabs open.

Histogram of tabs open on navigation

Not too surprising — the most common number of tabs to have open is one, with a pretty steady descent down to 9. It flattens out and hits a valley at 13, but then rises slightly again for a second peak at 16. So, again we see a slight bi-modality to the distribution. But if we take the same set of “tab power users” from the first graph, we see that they have roughly the same profile as all the participants put together. In fact, the peak at 16 is almost entirely caused by only two of the power users: participants 14 and 20.

One possible explanation for the bi-modal distribution here is tab bar scrolling. At a typical screen size on a laptop or desktop, the tab bar can fit about 9-13 tabs without scrolling. Many people probably try to avoid having the tab bar scroll, but once you get to the point where it starts scrolling, there’s little additional cost to having more tabs open. So it may be the P14 and P20 are the only ones comfortable with keeping so many tabs open that the tab bar is scrolling.

Take a look at the median and max number of tabs that each participant had open:

Graph of median and max tabs

(Note that there’s no participant 8…he’s the one that dropped out.)

Participants 14 and 20 definitely stick out — it’s easy to see why they contributed so much to the yellow portions of the previous chart. Participant 14 by far the highest median number of tabs open with 17, while no other participant had a median higher than 6. Participant 20 actually edges out P14 for max tabs though, with 42. (For once it really is the answer.) Forty-two — that’s a lot of tabs! The tab bar would be scrolling two are three times over at this point. He actually commented on this, saying “Now I am opening tabs up from Digg and they are appearing at the end of my massive list. This is truly a bad way to browse.”

P19 is an interesting one…a median of only one tab open, but a max of 27! Participant 2 is similar, but not nearly as extreme: a median of 4 and a max of 20. Even if these two preferred not to have too many tabs open most of the time, they weren’t afraid of opening up lots of tabs when they needed to.

In general though, it looks like most people don’t go far beyond where the tab bar starts to scroll. I’ve marked a gray line on the graph at 13 tabs. At a resolution of 1280x1024, this is the point at which the tab bar starts scrolling (on my computer, at least). We see one person who maxes out at 13, and a few more who max out at 14. In all, there are 9 people whose maximum is between 10 and 14.

Conclusions

There are a few things we can take away from this. First, we saw that people who use tabs heavily can create 2 to 3 times as many tabs as other users. It’s not obvious what the cause for the bi-modality in the distribution is though. From the second and third graphs, we see that having 10 or 11 tabs open is not that uncommon, even for people who aren’t “power users”. And the third chart also show us that even people who don’t have many tabs open on average can sometimes have spikes of a large number of tabs.


Let me know if you have any questions or feedback. Have I explained things clearly? Are there any other numbers you think I should take a look at? Leave me a comment or send me an email. I’ll be posting some other interesting results from my study over the next couple of weeks.


21 Comments:

  1. Liz Blankenship - April 14, 2009:

    Hey Pat, Really excited to see the results start coming in, as this makes the case for our TabViz project even stronger. I know this isn't in the context of the study you did, but I think it would be incredibly interesting to see how people's behavior changes over time - say, from their first introduction to tabs, to becoming a frequent Ctrl-Click to open a link in a new tab sort of user.

    I'm not sure if you have the capability to definitely distinguish the source of a tab, but another thing that would be interesting to consider in the data examined here would be how many of those tabs were actually consciously created by the user - i.e. ctrl-click or File->New Tab/Ctrl+T rather than a link that upon normal click generated a new tab.

    Can't wait to see what else you find! Liz

  2. Jakob Hilden - April 14, 2009:

    I agree, that this is really interesting to look at.

    One thing that I think could be highly relevant, would be if you could plat the number of open tabs over time. So you could see if tab just accumulate over time or if a lot of them are opened at the same time. You could also see when tabs are getting closed. Maybe there is a certain limit at 9-13 tab where people that don't want the tab bar to get out of hand starting closing tabs?

    I think time is a very important factor here.

    Overall, this is absolutely great research, I hope you are planning on continuing it or that others are picking it up.

    --Jakob

  3. Patrick - April 20, 2009:

    @Liz: I can tell with a pretty high confidence how the tab was opened. Almost with a 100% certainty when it was triggered by the user (via Ctrl-click, right-click, Ctrl-T, etc.), but when it's caused by javascript etc., it can be more difficult to tell.

    @Jakob: Yep, it would definitely be interesting to see the number of tabs open over time. It would be a lot of data to look at though, and I'm not sure what kind of conclusions we'd be able to draw. Definitely worth looking at though.

  4. Kevin McGuire - April 27, 2009:

    Great to see this research! I've always wanted a concrete usability study for editor tab usage in Eclipse. Discussions tend to be anecdotal, filled with strong bias, or based on unsubstantiated usage assumptions.

    Our current management policy of displaying them in MRU order has folks who love or hate it. It was an attempt based on a theory of relevance which I'm not sure is true, or at least true for everyone. As with your Firefox study, I believe that our vast types of Eclipse users have different usage patterns and needs when it comes to tabs.

    Underlying the data is a question of "why". Why do people open new browsers instead of new tabs? Why is there a bimodal split? Is there some cog sci explanation for ability of computer scientists v.s. non to hold that much data in their heads? What about the relationship between the tabs? How do tab groups in IE8 come into play? Could we use similar in Eclipse?

  5. ziczac - April 27, 2009:

    I would like to know how many users actually are using tabs anyway. You were looking for users that "use Mozilla Firefox for several hours a day, and often use multiple tabs or windows". But how surfs the average user? How does a MS Internet Explorer- or Safari-User surf, even when his browser support tabs? And how is their usage of the back-and-forward-navigation? I think it is very different from your test group.

  6. Patrick - April 30, 2009:

    @Kevin McGuire: It would be really interesting to see a similar study for tab usage in Eclipse. The usage patterns would definitely be different, although I think a lot of my findings will still be applicable.

    As for the "why", that is something that my study addressed. I'm hoping to publish my full findings at CHI, but in the meantime I'll try to post some of the more interesting qualitative results here.

    @ziczac: You're right, it would be interesting to get an idea of what "average users" do, but this wasn't the goal of my study. That said, most of the people in my study were not typical "power users", although you're right that it's a biased sample because I asked for people who use multiple windows and tabs heavily.

  7. Lisa S - May 4, 2009:

    Very interesting. I'm curious if all of your participants were male? I would be very curious to see the differences between men and women.

    I am a very heavy tab user but mainly because I multitask a lot of different "roles" through the day (mom, at-home business, leader of various online/in person groups, hobbies, homemaking) - I always have tabs that I want to come back to, as a placeholder. I might have various FB tabs, news articles (usually clicked through twhirl or FB), recipes, a couple google doc windows for business and/or personal etc, waiting hopefully for me to return and read them sometime (all getting reloaded each time I have to shut down FF, to the dismay of my husband and my RAM usage).

    As for the scroll limitation, I usually end up going to a new window for a new set of "permanent" tabs. If I were able to drag tabs between windows I would keep them organized; I do now to some extent but they always get mixed up.

    I wonder if either the multi-role issue or the trying to keep track of lots of things at once effects women more than men.

  8. Screwtape - May 4, 2009:

    Were the results controlled for tab-browsing add-ons? As a heavy tab user, I've got the "Tree Style Tab" add-on installed which (amongst other things) lists the tabs down the side of the browser instead of across the top. You might only fit nine or ten tabs across the screen without scrolling, but you can fit perhaps two-dozen stacked vertically.

  9. Patrick - May 5, 2009:

    @Lisa S: Actually, about 3/4 of my participants were female. I thought it might be interesting to look at the differences between men and women, but it's a pretty small sample size, and there would be too many confounding factors.

    @Screwtape: I did ask all my users what extension they had installed. The only tab-related extensions that anyone had were Tabs Open Relative, and Tab Aging. Those might affect tab usage somewhat, but probably very little, especially compared to something like Tree Style Tabs.

  10. Eric Nakagawa - May 6, 2009:

    I have 66 tabs opened. I laugh at your data!

    Actually, I find myself in this never-ending struggle to manage my opened tabs. Delicious helped for a bit... but the # always creeps up the longer I work on a project. Sometimes memory corruption and complete loss of tabbed data and history is a godsend.

  11. Jing - July 14, 2009:

    Awesome study, I've been wishing forever for some data on tab usage!

    Some things that would be really interesting to see as followup studies (not holding my breath for it though ^_~): - patterns in viewing tabs (like, opening many tabs in one go then viewing each, or viewing each as they open) - correlation between the method of opening tabs (click vs. keyboard) and the concurrent number of tabs open? - frequency of tab management actions such as moving, closing in batches, opening in new windows, etc.

  12. TabPower - August 16, 2009:

    Currently there are 207 Tabs open... am I crazy?

  13. Johan Strandell - September 17, 2009:

    Is the median and max number of tabs calculated per window or for all windows that the user has open?

    For instance, in this browser window I only have 2 tabs open at the moment, but in all windows there's at least 25 in total.

    I think that's another dimension to take into account: you can be a fairly heavy tab user, while not going above 5-6 tabs per window.

    But very interesting study, regardless!

  14. Emile - October 13, 2009:

    Maybe I missed it, but I do not see where motivated Firefox browser as your browser for your study? I would assume it's due to its open and extensible nature, but was there any other reason?

    P.S. I am a heavy multi-browser, multi-tab user.

  15. Patrick - October 13, 2009:

    Yes, the main reason that I chose Firefox was its extensibility. However, although IE has much more market share than Firefox, many IE users are still on IE 6, which doesn't support tabs.

  16. Charlie Martin - October 15, 2009:

    I'm one of those users like your #14 — right now I have 5 windows open, with between 5–13 tabs each — and I've got to say that I'd use even more if the damn browsers didn't grow increasingly slow an unstable. I've developed workflows for this, by opening a succession of tabs and then closing them in order as I read the pieces I want, but I wonder how much of this result is being driven by degradation of the experience with large numbers of tabs.

  17. Vic - February 20, 2010:

    Just want to contribute to this, I have average 10tabs within 1 window. I try to keep it around 10 so that they are still on the tab bar and not in a drop down list. On average I have around 15tabs open, but this can grow to 90tabs when I'm doing research.

    oh, and I am a Safari user on OS X snow leopard :)

  18. Edward Keogh - June 5, 2010:

    Dear Patrick,

    I am interested in how people use a browser in the first instance, regardless of 'tabbing'.

    Most browers are accessed and used with a simple 'search terms' interface using ta simple box type search facility. Few people bother to use any advanced search options, let alone boolean structures in their search terms.

    In short, most people seem to do 'quick and dirty' searching, resulting in vast numbers of returns and so give up looking for what they really need.

    As a librarian, now retired, but still asked for help in information provision using the Web, not browsing but help ib structuring search patterns such qualatative data would be helpful.

    Regards

    Eddie Keogh

  19. Edward Keogh - June 5, 2010:

    Dear Patrick,

    I am interested in how people use a browser in the first instance, regardless of 'tabbing'.

    Most browers are accessed and used with a simple 'search terms' interface using ta simple box type search facility. Few people bother to use any advanced search options, let alone boolean structures in their search terms.

    In short, most people seem to do 'quick and dirty' searching, resulting in vast numbers of returns and so give up looking for what they really need.

    As a librarian, now retired, but still asked for help in information provision using the Web, not browsing but help ib structuring search patterns such qualatative data would be helpful.

  20. Seun O - August 20, 2011:

    I currently have 62 tabs open on firefox; I'm using chrome with seven tabs open. The open tabs are changed frequently as well. So I guess I would be on the extreme side of the bell curve.

  21. Dave Kaufman - Techlife - October 14, 2011:

    Your study is awesome...and was a last minute addition to my syndicated column Techlife's article "The Tab King".

    The link is probably the funniest ever, as I had already written "there is no hard and fast data on tab usage" and then I found your info in a second pass, so put the link under "there is" as a tribute to your work.