Testing Web Navigation with Card Sorting & Tree Testing

Websites, apps, software, any product with a menu needs a way to get around. While your navigation can be fun, creative, or at times unorthodox, it always needs to be functional first. When discussing usability testing for information architecture, you’ll often hear about the two most effective tests: card sorting and tree testing.

Both tests are simple and easy to conduct, and both tests yield vital data to maximize the organization of your site. Card sorting comes before you create your structure, so you can understand how your users naturally organize your site. Tree testing comes after, as a way to validate your success or point out room for improvement.

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Card Sorting

The beauty of card sorting is in its simplicity. All you do is write the different elements of your product on note cards or Post-It notes, then have your participants organize them in a way that makes the most sense to them.

If that’s even too much to handle, you you can also go with a usability testing tool like OptimalSort, which can analyze the data for you. Either way, the result gives you a solid understanding of how your target users would intuitively navigate your product.

card sorting

Card Sorting Variations

There are a few different strategies to card sorting, depending on your needs. Donna Spencer, card sorting expert and Founder of Maadmob, shares her personal experience in an article for Boxes and Arrows. For such a simple activity, there’s plenty of variation and controls that will affect the kind, and validity, of data you receive.

The initial distinction to make is open or closed, explained below:

Open Sorting – Users are provided only with the elements cards, and then are left to group them however they see fit. Once grouped, users are asked to give names to the groups themselves. This is recommended for generating new ideas since you can work backwards from the users’ natural thought processes.

Closed Sorting – As with open sorting, users are given the elements cards; however, they are asked to categorize them into predefined groups. This is recommended if you’re working within the restrictions of pre-existing categories, as with updating an already developed website structure.

Open vs. closed is the primary decision, but there are other methods for varying your results:

Groups vs. Individuals – Groups allow users to work collaboratively, for better or worse, and can help you learn about multiple users at once; however, group dynamics might affect your results.

Remote vs. On-location – Online software tools allow you to test more users in a faster time, yet you’re unable to directly observe their decision-making processes. On-location gives you a fuller understanding of how your users came to their decisions, but requires more planning and scheduling.

Card Sorting Guidelines

Of course there’s room for customizing your card sorting, but William Hudson, UX Strategist and Consultant, lists some general benchmarks that can apply to any method you choose. Most useful, he lists the approximate times you can expect people to sort a given number of elements:

  • ~20 minutes for 30 elements
  • ~30 minutes for 50 elements
  • ~60 minutes for 100 elements

Using this time structure, you can plan out in advance how long the tests will take to administer, once the cards are written or the software established. However, in our personal experience, these guidelines are a bit generous one of our closed card sorts involved 47 cards and four categories, but only required an average of three minutes to complete.

Another universal rule is to avoid complex language on the cards. Big words – at least words with many syllables – and technical jargon run the risk of confusing the test-takers, or them misinterpreting the meaning. While simple wording is good advice in general for the language usage of a product, it’s essential for card sorting since overly complex labeling will disrupt the natural thought processes.

A lot of experts agree on the merits of card sorting. Pierre Croft, IA and UX expert for Decibel Digital encourages card sorting because it can help deflect the bad ideas of HIPPOS (highest paid people in the room) who might not know how to build a good website. He also lists out some pointers to keep in mind when preparing your test:

  1. Don’t mix parent and child categories – In other words, use categories from the same level, or else you will confuse your participants.
  2. Have blank cards and pens handy – While this is a standard procedure for open card sorting, it’s also quite useful for closed card sorting. After the formal testing is done, you can provide a couple of blank cards for participants to write down additional categories. While the information might be “off-the-record,” it could bring to light some useful insights.
  3. Don’t intervene – Intervention will obscure the data, so avoid the temptation. Of course give the test-takers some guidance if they’re confused, but only for issues not related to the results.
  4. It’s OK if users don’t group everything – A lack of grouping can be just as telling as a fully complete one. If this happens, make sure you ask the user why. If you’re running a closed sort and not everything is sorted, you can also provide blank cards to see why the existing categories weren’t chosen.
  5. Set time limits beforehand – This makes scheduling easier in general and gives the participants an idea of how much time to spend on their tasks.
  6. Limit your cards – If your website has hundreds or even thousands of pages, you can choose only first and second-level pages to keep things manageable. For example, “Contact Us,” “Terms of Agreement,” and other utility pages can be omitted since they can be found on almost all websites out there (so you wouldn’t really be testing anything unique to your site).

Tree Testing

On the opposite spectrum of card sorting, tree testing allows you to test the information architecture after its designed. Tree testing works by stripping out the visual elements of your navigation system to see how the basic structure fares on its own. With a tree test, you examine only the labelling and hierarchy of your content.

Martin Rosenmejer of Webcredible calls tree testing one of the most important steps early in the design process. In a nutshell, a tree test involves participants finding different information on a clickable sitemap (or “tree”).

Using a usability testing tool like Treejack, you then record task success (clicking to the correct destination) and task directness (certainty of users that they found what was needed). It’s a foolproof method for seeing how well your users can find their way around your product.

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As displayed above, when we redesigned Yelp’s website, we provided a tree representing the support site and then gave users 10 tasks (for example, finding information on what to do with bad reviews). Because the overall task success rate was 53% and directness was 46%, we knew that the IA needed changing – but we knew exactly where to make those changes.

Simply put, a site search bar (or a three-line hamburger menu) is just not enough if the navigation is poor because users won’t know what is available to search. The rule of thumb for web design is to make the user think as little as possible, because searching requires users to recall from memory, it negatively affects the UX.

If we’ve sold the idea of tree testing on you already, Jeff Sauro, Founding Principal of MeasuringU, goes into details about how to properly run them. He explains that tree testing is used primarily for two reasons:

  1. Determine a product’s searchability – How well can users navigate the site, and what areas cause the most problems with navigation?
  2. Validate a change – Did a recent update correctly fix the problem, or are further revisions necessary?

Tree testing is, at heart, a statistical test. As with other quantitative tests, the data will be more accurate with more participants. How accurate? Check out this chart to find the smallest margin of error within your means; we recommend aiming for 20% error or better.


We can’t stress enough the importance of information architecture – if the content isn’t structured logically with a simple flow, it might as well not exist. That’s why these early tests can help identify and solve the problems before they actually become problems.

The strength of tests like these is that the data is modeled after the users’ natural behavior, and when it comes to testing your IA, no tests do it better than these two.

Now Read: 7 Steps to Better Website Feedback