September 2, 2008
Site Map Usability
by Jakob Nielsen
Dr. Nielsen founded the “discount usability engineering” movement for fast and cheap improvements of user interfaces and has invented several usability methods, including heuristic evaluation. He holds 79 United States patents, mainly on ways of making the Internet easier to use.
New user testing of site maps shows that they are still useful as a secondary navigation aide, and that they’re much easier to use than they were during our research 7 years ago.
One of the oldest hypertext usability principles is to offer a visual representation of the information space in order to help users understand where they can go. Site maps can provide such a visualization, offering a useful supplement to the primary navigation features on a website or intranet.
A site map’s main benefit is to give users an overview of the site’s areas in a single glance. It does this by dedicating an entire page to a visualization of the information architecture (IA). If designed well, this overview can include several levels of hierarchy, and yet not be so big that users lose their grasp of the map as a whole.
We define a site map as a page intended to act as a website guide. The site maps we studied took a variety of forms, including alphabetical site indexes, dynamic diagrams, and two-dimensional lists. The term “site map” here thus encompasses a wide array of features, appearances, and names, including “guide,” “overview,” “index,” and “directory.”
Two Research Studies
To find out how people use site maps, we conducted two rounds of usability research, testing a range of site map designs with users as they performed representative tasks. A total of 30 users participated in our site map testing, with 15 in each of the two research rounds.
We tested the following 20 websites, which included a mix of e-commerce and marketing-oriented sites, high-tech companies, B2B sites, content sites, non-profit organizations, and government agencies.
| Sites Tested In Study 1 | Sites Tested In Study 2 |
|---|---|
| CDNOW (e-commerce) Documentum (high-tech product) Interwoven (high-tech product) Mercedes Benz USA (marketing site for cars) Museum of Modern Art (non-profit) New Jersey Transit (local transportation) Novell (B2B) Salon (online magazine) Siemens Medical Solutions (B2B) United States Treasury Department (government) |
Administration on Aging (government) BMW USA (marketing site for cars) Citysearch Boston (visitor info) Harvard Pilgrim (health insurance) iRobot Corporation (high-tech/e-commerce) The Knot (wedding information/e-commerce) Marriott (hotels, with online booking) Scholastic (children’s books) Texas Roadhouse (restaurant chain) TiVo (high-tech product) |
In both studies, we first took users to a site’s homepage and gave them a task without any special mention of the site map. This part of the research assessed the extent to which users naturally turn to site maps. Later in each study, we specifically asked users to go to the site map if they hadn’t already gone there on their own.
Study 1 was conducted 7 years ago. Comparing the two studies thus allows us to assess long-term trends in site map usability.
Site Maps are Used Rarely
People rarely use site maps. In Study 2, only 7% of users turned to the site map when asked to learn about a site’s structure. This is down from 27% of users in Study 1.The good news is that users can actually find the site map in those few cases where they want to. In Study 2, 67% of the users successfully found the site map when we asked them to “Find a page that lists every part of the website.”
Keep It Simple
The two main usability guidelines for site maps are:
- Call it “Site Map” and use this label to consistently link to the site map throughout the site.
- Use a static design. Don’t offer users interactive site map widgets. The site map should give users a quick visualization without requiring further interaction (except scrolling, if necessary).
These guidelines are unchanged from the report’s first edition. Dynamic or interactive site maps caused horrible failures 7 years ago, and they still caused trouble in Study 2. The site map’s goal is to give users a single overview of the information space. If users have to work to reveal different parts of the map, they lose that benefit. A site map is, after all, a map; it should not be a navigational challenge of its own.
As we’ve found repeatedly, users hate non-standard user interfaces that force them to learn a special way of doing things for the sake of a single website. Site maps should be simple, compact layouts of links, and they should show everything in a single view.
The one small complexity we recommend is to use a multi-column layout. In Study 2, users easily succeeded with 61% of tasks involving multi-column site maps compared to 47% of tasks with single-column site maps.
Multi-column site maps worked better because users needed less scrolling to get an overview of the site’s structure. People were more likely to become lost within long, scrolling site maps. They typically scrolled up and down the map multiple times, often accidentally or purposefully skipping content. In fact, users often started with one quick scan of high-level categories, then scrolled back up and did a more detailed search, sometimes repeating this process multiple times with more and more focus each time. In contrast, multi-column site maps made it easier for users to quickly glance at all categories and subcategories, and thereby get a lay of the land before digging deeper.
Why Have a Site Map?
Seven years ago, 48% of the 50 websites we surveyed had site maps. Today, 71% of the 150 websites we surveyed had site maps and 59% of the 56 intranets analyzed in our report on Intranet Information Architecture had site maps. Also, most site maps have become somewhat more usable during the time between our two research rounds.Despite the prevalence of good site maps these days, users don’t use them very much. So why bother making a site map for your website? Because it can help users understand your site and what it offers.
I still recommend site maps because they’re the only feature that gives users a true overview of everything on a site. One could argue that a site’s navigation serves the same purpose. For example, some navigation offers drop-down menus that let users see the options available in each site section. But even with these menus, users can see only one section of content at a time.
A site map lets users see all available content areas on one page, and gives them instant access to those site pages. Site maps can also help users find information on a cluttered site, providing a clean, simple view of the user interface and the available content. Site maps are not a cure-all, however. No site map can fix problems inherent in a site’s structure, such as poor navigational organization, poorly named sections, or poorly coordinated subsites.
If site maps required a major investment to design, they wouldn’t offer sufficient ROI to be worth doing. But because all of our guidelines call for site map simplicity, making a good one doesn’t require a lot of work, and it will help some of your users. More importantly, it will help users at a critical time: When they are lost and might abandon your site if they don’t get that last piece of assistance to find their way around.
Site maps are a secondary navigation feature — a humble role that they share with breadcrumbs. Indeed, the arguments in favor of site maps are the same as the arguments for breadcrumbs:
- They don’t hurt people who don’t use them.
- They do help a few people.
- They incur very little cost.
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