Part of making a site easy to use is organizing information so that the site’s visitors can find what they’re looking for without much effort. All too often content is structured based on what makes sense to the company, not to the visitors. But among many UX research methods, there is a simple technique that can help teams properly organize the content. This technique is called card sorting.

What is card sorting

Card sorting is a UX research technique for discovering how people understand and categorize information. This technique is used when a team wants to group and label website information in a way that makes sense for the target audience. Card sorting creates a foundation for robust information architecture (IA), and strong IA allows for the creation of a navigation system that matches users’ expectations.

Card sorting is useful in two cases

  • When you want to discover how people understand and group different concepts. You want to reveal the user’s mental model, and this understanding will help you design better products for them.
  • When you want to improve the existing design or create a new design, your goal is to understand how users categorize information and make the UI predictable for them.

What does a card sorting session look like?

To conduct a card sort, you need two things—actual users and cards. For cards, you can use actual physical cards (pieces of paper) or one of several online card-sorting software tools like Optimal Workshop or Userzoom. You need to choose a set of topics and put each topic on an individual card. You ask the user to look at the cards one at a time and place cards that belong together into piles. At the end of the session, you will have all the topics organized into groups.

Practical tips on how to conduct effective card sorting

Analyze the information you have

Before doing a card sort, you need to understand what information you have on your website. That’s why the first step is conducting a content audit on your website, prioritizing all the content, and selecting the most relevant items for the session. Everett Sizemore wrote an excellent step-by-step guide on how to conduct a content audit. He also provides a sample content audit spreadsheet that you need to fill out at the end of the audit.

Content audit spreadsheet with columns for url, title, action, details, page type.
A content audit spreadsheet filled with the actual data. Image by moz.

If you’re working on a brand new website, you should brainstorm and mind map all the information you want to include on it.

A mindmap of a website includes homepage, sub-pages, headers, sidebars and footers.
Mindmap of the website. Image by creately.

Select the appropriate type of card sorting

There are three card sorting UX techniques you can choose from — open, closed, and hybrid.

Open card sorting

In open card sorting, each participant is given a stack of cards that are pre-filled out with topics and then asked to group those cards any way they want. After that, the participant needs to create labels for the groups that they chose. Participants don’t have any restrictions for naming.

This type of sorting is great when you want to design a new website or improve the existing one. By analysing card sorting results, it’s easy to see whether the website structure that you have right now matches up with how people would organize the same information.

Illustration of an open card sort starting with cards, groups of cards and then labeled cards.
Open card sorting. Image by Interaction Design.

Closed card sorting

In closed card sorting, the researchers create labels for categories and asks participants to sort cards into predefined categories. All participants must do is match content to existing categories. This type of card sorting doesn’t reveal how users conceptualize topics, but it helps you understand how well an existing category structure supports the content.

Closed card sorting works best for prioritizing and ranking features. For example, you can apply it for search filters in the eCommerce app. Users can distribute all search filters you have in groups ‘Mandatory’, ‘Optional’, or ‘Frequently used’ to ‘I never use it.’

It’s not recommended to use card sorting for evaluating navigation structure. Instead, UX researchers recommend using tree testing because this technique is more suitable for evaluating navigation categories.

Closed card sorting with stack of cards then grouped into pre-defined categories.
Closed card sorting. Image by Interaction Design.

Hybrid card sort

As the name suggests, this type of card sorting where participants sort cards into predefined categories but also can create their categories.

Hybrid card sort works the best when researchers want to generate ideas for grouping information, and they know that they have some missing categories in their current category structure. They can gain insights about missing categories, and this information can inform design decisions.

Select appropriate format for card sorting

Moderated vs. unmoderated

Unmoderated card sorting involves participants organizing content into groups on their own. Usually, such sessions are conducted online with tools like User Zoom and don’t require facilitators. It’s a cheap and fast way to collect information about user behavior. The major downside of this method is the amount of work required to analyze the session results (it can be hard to understand the rationale behind the decisions).

Moderated card sorting requires having a moderator. This type of card sorting can provide more valuable insights because the moderator can also debrief the user—ask users to explain the rationale behind the groups they created. Questions like “Why did you place this card into this group?” can reveal the rationale for the grouping. This type of card sorting is more expensive and might require an additional budget.

Paper vs. digital card sorting

In paper card sorting, topics that are written on sticky notes. The low learning curve is a significant advantage of this type of sorting. Participants don’t need to learn new software to complete the task; all they have to do is to stack paper into piles on a table. It’s also easier to experiment with physical cards—they can move cards around with ease, write some notes on the card and start all over again whenever they want. The downside of this method is the amount the work the researcher has to do in order to document the participant’s decisions.

Two men using index cards doing a card sorting exercise on a table.
Card sorting UX practice using paper cards. Image by Zurb.

Digital card sorting tools are web-based services were the participants use digital representations of cards and drag & drop them into categories. Digital tools provide a significant benefit for researchers—the software will analyze participant’s actions and create reports for researchers automatically. But might not be the best option for participants because they will need to learn how to use the tool, and also the tool can limit their actions (it can prevent them from creating categories, or making a specific grouping).

OptimalSort is an tool that lets you group content into groups online for virtual card sorting sessions.
Card sorting UX practice in OptimalSort.

Well-designed cards

Every card should represent a single concept and can be grouped

What should you put on cards? While there are no hard and fast rules, it’s recommended to make cards meaningful for participants. Test cards with your audience to ensure that participants understand the meaning of information on a card and cards are groupable. Inconsistent and unrelated cards will prevent users from creating coherent groups.

Don’t go overboard with the number of cards

When you select topics for your card sorting session, aim for something in between 30 and 60 cards. This number will help you gather enough useful data to make informed decisions about your product and won’t overwhelm participants with too much information.

But don’t limit yourself with this number right from the start. Start by opening a spreadsheet and collecting all the possible concepts or items you could include in your card sort. Create as much as you want, then evaluate them. Include only the most relevant cards and discard the rest.

Acknowledge the unknown

If the participant isn’t sure about a card or doesn’t know what it means, it’s okay to leave the card off to the side. It’s better to have a set of or “uncategorized” cards than randomly group cards.

Be careful with text on cards

Jakob Nielsen advises against using topics that contain the same words because participants tend to group those cards. He illustrates this problem using the following sets of cards:

A table showing the same topic grouped different ways.
Avoid using sets with synonyms (like this one). Image by NNGroup.

Given the set A, most participants will sort all “strawberry” cards together and all “wheat” cards together. Likewise, given the set B, most users will sort cards by activity “Planting,” “growing.”

Include images

Images can be as useful as a text for representing concepts and items. You can include pictures to illustrate or clarify the text on your cards

Recruit participants

For card sorting, it’s recommended to hire participants who represent the demographics of your intended users. The number of participants depends on the format of the card sorting. For in-person, moderated card sort, you need to hire 15 participants. It will be enough to give you invaluable qualitative insights.

Don’t use card sorting as a replacement for usability testing

Card sorting is not a tool for testing usability. The goal of card sorting sessions is to discover how people think about and make sense of your information, not to understand whether they can or cannot find it in your design.

Books about card sorting

If you’re interested in learning more tips for running effective card sorting sessions, I highly recommend reading the book Card Sorting: Designing Usable Categories by Donna Spencer. In her book, Donna shows how to plan and run a card sort, analyze the results, and apply the outcomes to your projects.


Card sorting is a highly useful technique in information architecture; it is used to understand how users think about your content. It can help you organize content so that it suits your users’ mental models, rather than the point of view of your company. Learn more about how you can benefit from other tools like creating a sitemap and website navigation.