Card Sorting in UX Research

Learn how to effectively organize information and improve usability through user-driven categorization
Card Sorting in UX Research Lesson

A designer’s main goal is to ensure users can find information in a system and navigate it without a hitch. The card sorting method is the perfect tool to build your product’s information architecture from scratch or to adjust the existing one to suit your users' expectations.

Card sorting is a fantastic low-cost and quick UX research method to help teams organize and prioritize content effectively. However, it's not a one-size-fits-all solution. You should explore the pros and cons of other methods to select the one that best fits your needs. We also recommend combining findings from different studies to improve user experience and create a functional and user-friendly product.

Purpose of card sorting

Card sorting is a UX research method for building an intuitive information architecture or evaluating the existing one. Within this study, researchers ask participants to organize individual labels written on notecards, pieces of paper, or using an online card-sorting tool (e.g., Miro) and group them into logical categories.[1]

This technique helps teams understand how users perceive content and organize it to fit their mental models. You can also run a card sorting session when you want to learn what kind of language your audience uses to talk about your product and use these words for your labels.

The disadvantages of this technique include:

  • Labels are used out of context. Users navigate interfaces relying on visual signs, and notecards with labels may not be enough to understand a website goal.
  • The analysis takes time. The analysis of study findings can be time-consuming, especially if results are inconsistent.
  • The findings may not go deep enough. Users may rely on categories differently when performing tasks. Thus, your analysis might only provide an overview of the problem without revealing the details.

Pro Tip! You can use card sorting methods to compare mental models between user groups and learn how they perceive your content.

List your cards

Before collecting cards for your card sorting session, consider conducting a content audit. This is a method for inventorying your existing content and selecting the most relevant items. If yours is a brand-new product or service, brainstorm and list all the information you want to include in your session.

Now, you can start listing groups for users to sort, group into categories, and label. The number of cards may vary between 30 and 60 or be slightly more. You can list all the possible cards and discard irrelevant ones. Too many cards will overwhelm users, prevent them from making informed decisions, and also make data analysis difficult for you.[2]

Avoid using cards with similar words or synonyms — it may confuse users, and they'll end up grouping these cards together.

Pro Tip! Make sure one card includes only one topic.

Users sort topics

Once the topics are ready, shuffle the cards and ask participants to organize them into piles any way they want. Don't rush the participants and give them 15-20 minutes to complete sorting. If they haven't finished after 20 minutes, give them an extra 5 minutes.[3] Assure participants they can move cards around if they change their mind about where a card belongs.

If users aren't sure about a card or don't know what it means, let them place the card in the "uncategorized" or "unsure" category instead of randomly grouping cards.

Pro Tip! Don’t instruct participants to sort a precise number of cards into a pile. It's okay if some groups are larger or smaller than others.

User mental models

A mental model is the explanation users have of how a system works or how they think it works. Ideally, users' mental models should be close to reality, as they make predictions and adjust their behavior based on their beliefs. According to Jakob's Law of Internet User Experience, users spend most of their time on other sites, which means they expect yours to work similarly.[4] When a website's navigation is too different from what people expect, they feel confused and may abandon the site out of disappointment.

Another dilemma is that each individual has a different mental model, and designers are no exception. Their mindset of how things should be in a system can radically contradict users' standpoints. Thus, a designer's prime goal is to create intuitive and valuable interfaces that meet users' expectations.

The card sorting method is a tool that indicates the gaps between designers' and users' mental models. Based on how users group items, designers can make conclusions about users' thinking and build intuitive information architecture that users understand at a glimpse.

Users name topic groups

Once participants have finished sorting cards, ask them to unleash their creativity and name the groups they've created. This naming step should go after users finish creating groups so that participants rely on their own mental models.

You may have ideas about names for categories, but it doesn't mean they will meet users' expectations. When interacting with a product, users tend to click straightforward, familiar labels and explore a product. If you insist on using your own categories without considering users' opinions, they'll likely ignore the unknown labels and avoid clicking them.

This doesn’t mean you should take the group names users suggest without a second thought. Use their ideas to experiment and come up with even better options.

Debriefing users Bad Practice
Debriefing users Best Practice

Once users have finished sorting cards, debrief users about their experience.

Some questions you may want to ask are:

  • Which cards were the most difficult to categorize?
  • Which cards might belong to several groups?
  • Why have they left a few cards unsorted?

The debrief session may help you understand users' mental models and the rationale behind their decisions. Asking users to think aloud during the card sorting session is another way of getting into users’ minds. The only concern is that subconsciously, people may want to please you with their answers. To avoid such biases, watch your body language and avoid showing any emotions while participants talk.

Pro Tip! Avoid asking leading questions or judging their performance.

Getting practical group sizes Bad Practice
Getting practical group sizes Best Practice

During the first sorting, avoid placing any restrictions on users. However, once the first session is done, you might ask users to take a step back, debrief them, and ask them to rearrange groups more practically. You may ask them to divide large groups into smaller subgroups or join small groups into larger categories according to your requirements.

Analyze card sorting data

Analyzing is the most time-consuming part of the card testing process. When performing exploratory analysis, you receive a more general overview of the collected data and insights.

When looking for common patterns of card sorting or naming categories, ask yourself questions like:

  • Which items often appear in the same group?
  • Which categories often use the same name?
  • Which items often stay uncategorized?

If you have a larger group of participants and are more interested in numbers, conduct a statistical analysis. You can fill out a spreadsheet and analyze data manually.[5] Otherwise, you can utilize an online application like Optimal Workshop or UserZoom.[6]

Pro Tip! If you’re redesigning your existing information architecture, compare the card sorting testing results to what you currently have.

Open vs closed card sorting Bad Practice
Open vs closed card sorting Best Practice

When UX practitioners discuss the card sorting method, they generally imply an open approach. In an open card sort, users group items and then create names for groups they've made by themselves.

Using an open card sort, you can:

  • Learn users' mental models
  • Understand how they search for information on a website
  • Build new information architecture in a way users expect

Open card sorts are notably helpful for evaluating how multiple user groups perceive your content structure and find information. In a closed card sort, the category names are already predefined by researchers, and users are asked to sort cards out between these categories.

A closed card sort allows you to:

  • Evaluate the effectiveness of the existing labeling system
  • Identify which categories are excessive, unclear, or misleading
  • Rank and prioritize categories. For example, you can ask users to distribute menu actions on an email app (e.g., Reply, Forward, Archive, Delete, Mark as Read, Move to, etc.) in groups such as “Mandatory,” “Optional,” “Frequently used,” and “I never use it.”
Moderated vs unmoderated card sorting Bad Practice
Moderated vs unmoderated card sorting Best Practice

During unmoderated card sorting sessions, users distribute cards by themselves, which usually happens with online tools. It's an inexpensive and fast way to collect data about users' ways of thinking. The downside of this method is that you don't have a chance to hear users' thoughts when organizing cards. Thus, the analysis is more time-consuming.

A moderated card sorting implies having a moderator — a person who facilitates the session. This method provides more insights because a moderator can ask participants questions like "Which item was the hardest to categorize?" or "Why do you think this card belongs to this group?" This method is more expensive and requires more planning.[7]

If you need to run a card sort with a large sample size, you can save your company's budget by mixing unmoderated and moderated methods. Run a few moderated studies to hear users' thoughts and conduct unmoderated studies with the rest to gain more statistical proof.

Paper vs digital card sorting Bad Practice
Paper vs digital card sorting Best Practice

Paper card sorting uses traditional paper index cards or sticky notes that users can organize in any way they like. Users don't need to learn how to use a new tool — they just group items into piles and name categories.

  • The pros: It's much easier to experiment with physical cards, move them around, or start over the whole process.
  • The cons: Researchers must manually create cards and record each participant's groups into a tool for analysis.

Digital card sorting implies using an online tool where the participants use digital cards and drag & drop them into categories.

  • The pros: The software collects and analyzes all the data. Researchers can gain insights directly from these findings.
  • The cons: Online tools are less flexible and require time to learn. Plus, technical or usability issues can confuse users and prevent them from creating new categories or moving cards between groups.
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