Card Sorting: Open, Closed, and Hybrid

Information architecture is the practice of organizing, structuring, and labeling content so users can find information and complete tasks. Card sorting is the foundational empirical technique used to generate and evaluate digital taxonomies.

• Open Card Sort (Generative): Participants organize content cards into whatever groups make sense to them, and then name the groups themselves. Use this when starting from scratch to discover user mental models and vocabulary.
• Closed Card Sort (Evaluative): Participants sort content cards into pre-defined, established categories. Use this to test whether an existing navigation taxonomy accommodates new content items.
• Hybrid Card Sort: Participants are given pre-defined categories but are allowed to create new categories if existing buckets feel unnatural.

A card sort is only as good as its stimulus cards:

• Granularity: Aim for 30 to 50 cards. Fewer than 20 cards fails to surface organizational depth; more than 60 cards induces participant fatigue.
• Avoid Category Leaks: Do not include category names in card titles (e.g., 'Financial Account Settings' vs 'Change Billing Password'). If card titles share keywords, participants will group them mechanically by word matching rather than semantic meaning.
• Sample Size: For qualitative open card sorts, recruit 15 to 30 participants to detect meaningful statistical clusters on dendrograms.

Card sorting generates a taxonomy; Tree Testing evaluates whether that taxonomy actually works for real tasks.

In a tree test:

1. All visual styling, navigation menus, and layout graphics are stripped away.
2. Participants are given a plain text tree (sitemap) and a realistic task: 'Where would you find instructions to update your company billing address?'
3. Observers track directness (did they take the direct path without backtracking?), time on task, and success rate.