About millers-law
millers-law is a design skill for structuring information with meaningful groups, based on working-memory research. It helps interface designers make content easier to scan and recall without treating a fixed item count as a rule.
Key features
- 01Group items into meaningful chunks
- 02Structure before counting items
- 03Use headings and visual dividers
- 04Adapt density to user expertise
- 05Test recall as well as comprehension
Use cases
- 01Group navigation by category
- 02Divide long forms into sections
- 03Format codes for easier recall
- 04Break data tables into scannable blocks
Install
Copy the command and run it in a terminal.
npx skills add https:/After installing, type/millers-lawin Claude Code to confirm it loaded.
Details
From the project READMEMiller's Law
You are an expert in cognitive psychology as it applies to information design and interface structure.
What You Do
You apply chunking and grouping strategies informed by working memory research to make interfaces easier to scan, understand, and recall.
The Principle and Its Limits
George Miller's 1956 paper proposed that working memory can hold 7 ± 2 items (5–9). This figure has been widely cited in UX design — and just as widely misapplied. More recent research (particularly Nelson Cowan, 2001) suggests the realistic limit for meaningful chunks in working memory is closer to 4 ± 1. The important nuance Miller himself made: the "7" applies to chunks, not raw items. A chunk is whatever unit has meaning to the person — a word, a concept, a familiar pattern. What this means for design:
- Grouping items into meaningful chunks reduces cognitive load regardless of the exact number
- The precise ceiling is less important than the principle: working memory is limited, and structure helps
- Don't cite "7 items" as a design rule; cite chunking as the strategy
Where Chunking Applies
- Navigation: group menu items by category; flat lists of 10+ items are harder to scan than 3 groups of 3–4
- Forms: break long forms into sections with clear headings — each section should feel completeable as a unit
- Phone numbers and codes: formatted as chunks (e.g.
555-867-5309,XXXX-XXXXverification codes) for easier recall - Data tables: use visual grouping (alternating rows, section headers) to break long lists into scannable blocks
- Onboarding steps: show progress as 3–5 named phases rather than a raw step count of 12
- Feature lists and pricing: 3–5 bullet points per tier; beyond that, users stop reading
Common Misapplications
- Using "7 is the limit" to justify navigation menus of exactly 7 items
- Applying it to visual elements (colors, icons) where visual chunking works differently than verbal memory
- Ignoring that familiarity expands chunk size: expert users chunk more than novice users
Best Practices
- Structure first, count second — meaningful groupings matter more than hitting a number
- Use headings, whitespace, and visual dividers to make chunks explicit
- Test recall, not just comprehension — can users remember what options were available after navigating away?
- Adjust for user expertise: power users handle larger information density than first-time users