ux-heuristic

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Conduct heuristic evaluation of user interfaces using Nielsen's 10 usability principles. Use this skill when the user needs to audit a website, app, or interface for usability issues, prioritize UX improvements, or conduct a quick expert review without user testing — even if they say 'review this UI', 'find usability problems', or 'why do users struggle with our app'.

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Added on2026-04-15

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Heuristic Evaluation (Nielsen's 10 Principles)

Overview

Heuristic evaluation is an expert review method that assesses a user interface against established usability principles. It's fast (2-4 hours), cheap (no user recruitment), and finds 40-60% of usability issues. Use it as a complement to, not replacement for, user testing.

Framework

IRON LAW: Every Violation Gets a Severity Rating

Finding a violation is half the work. Rating its severity is the other half.
A cosmetic inconsistency and a critical workflow blocker are both "violations"
but require completely different response urgency.

0 = Not a usability problem
1 = Cosmetic only — fix if time permits
2 = Minor — low priority
3 = Major — important to fix, high priority
4 = Catastrophe — must fix before release

Nielsen's 10 Heuristics

#	Heuristic	Question to Ask
1	Visibility of system status	Does the user always know what's happening? (loading indicators, progress bars, confirmations)
2	Match between system and real world	Does it use the user's language, not system jargon? Are conventions familiar?
3	User control and freedom	Can users undo, redo, go back, cancel? Is there an emergency exit?
4	Consistency and standards	Are the same actions/words used consistently? Does it follow platform conventions?
5	Error prevention	Does the design prevent errors before they happen? (confirmations, constraints, defaults)
6	Recognition rather than recall	Are options visible? Can users recognize rather than remember?
7	Flexibility and efficiency of use	Are there shortcuts for experts? Can users customize frequent actions?
8	Aesthetic and minimalist design	Is every element necessary? Does extra information compete with relevant info?
9	Help users recognize, diagnose, and recover from errors	Are error messages helpful? Do they explain what went wrong and how to fix it?
10	Help and documentation	Is help available? Is it searchable, task-oriented, and concise?

Evaluation Process

Define scope: Which screens/flows to evaluate
Walk through the interface 2-3 times with different user tasks
Flag violations: Note each violation with heuristic #, location, description
Rate severity: 0-4 scale for each violation
Prioritize: Fix severity 4 and 3 first
Report: Organize findings by severity, not by heuristic number

Output Format

markdown

# Heuristic Evaluation: {Product/Feature}

## Summary
- Total violations found: {N}
- Severity 4 (catastrophe): {N}
- Severity 3 (major): {N}
- Severity 2 (minor): {N}
- Severity 1 (cosmetic): {N}

## Critical Issues (Severity 3-4)
| # | Location | Heuristic | Issue | Severity | Recommendation |
|---|----------|-----------|-------|----------|---------------|
| 1 | {screen/element} | {#N: name} | {description} | 3/4 | {fix} |

## Other Issues (Severity 1-2)
| # | Location | Heuristic | Issue | Severity |
|---|----------|-----------|-------|----------|
| ... | ... | ... | ... | ... |

Examples

Correct Application

Scenario: Evaluating a food delivery app checkout flow

Location	Heuristic	Issue	Severity
Cart page	#1 Visibility	No loading indicator when adding items — user taps multiple times	3
Payment	#5 Error prevention	No confirmation before placing order — accidental orders happen	4
Error screen	#9 Error recovery	"Error 500" with no explanation or retry button	4
Address form	#6 Recognition	User must type full address instead of selecting from saved addresses	2

Priority: Fix #5 and #9 immediately (severity 4) ✓

Incorrect Application

"The app looks ugly" → Not a heuristic violation. "Aesthetic and minimalist design" (#8) is about information hierarchy, not visual attractiveness. A specific violation would be: "Product page shows 15 data fields simultaneously, burying the price and 'Add to Cart' button."

Gotchas

3-5 evaluators find 75% of issues: One evaluator finds ~35%. Diminishing returns after 5. If possible, have multiple evaluators work independently then merge findings.
Heuristic evaluation finds problems, not solutions: It tells you what's wrong, not how to fix it. Solution design is a separate step.
Not a substitute for user testing: Experts predict user behavior imperfectly. Some "violations" that experts flag don't bother real users, and some real problems experts miss.
Mobile vs desktop: Apply heuristics separately for each platform. Touch targets, screen real estate, and interaction patterns differ significantly.
Accessibility is not a heuristic: Nielsen's 10 don't explicitly cover accessibility (color contrast, screen reader support, keyboard navigation). Add WCAG checks separately.

References

For WCAG accessibility checklist, see
```
references/wcag-checklist.md
```