What is the max number of usable categories in a taxonomy UI that has no search?

Question

At what point in size does it become unusable to select from a taxonomy list for an end user. I have a UI, used by the persona of John Q Web User, a user with no particular tech savvy who expects the UI to be fairly intuitive. This is not some admin or super user. When presenting this user with a list of taxonomy terms, in the form of cards, at what point does the number of terms become difficult to manage?

Our taxonomy today is too broad at 9 terms, but I am concerned that it will be too granular and difficult to navigate at 30 terms. Is there any research indicating a sweet spot that you know about?

Answer 1

I recommend doing something cheap to test. You can easily do this on paper using note cards or sticky notes even. Write your terms down and format them on the table the way you expect. You can also turn this into a card sorting activity.

Here are some questions I have.

• What do people do with these terms?
• How do people search through the list of terms without "search"?
• Do people need one or more than one term at a time?
• Do people think of the 30 terms as grouped together in some meaningful way? (potentially into 9 buckets)
• Are people doing this on a small screen or a large screen?