NielsenConsistency [principle] v1.0.0

Nielsen Heuristic 4: users should not have to wonder whether different words, situations, or actions mean the same thing; follow platform and industry conventions.

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

Attributed To

Jakob Nielsen, 1994

Applies To

• icon usage: same icon for same action across all screens
• color semantics: red = error/danger used uniformly, not decoratively
• keyboard shortcuts: matching OS conventions (Cmd+S, Ctrl+Z)
• terminology: using one term for one concept throughout all UI copy
• interaction patterns: identical controls behave identically everywhere
• component libraries: enforcing internal consistency via a design system

Counter Examples

• A SaaS product where the primary action button is blue in the dashboard, green in settings, and purple in onboarding — users lose confidence in which button is 'safe'.
• An app where Escape closes modals in some flows but does nothing in others — users can't form a reliable mental model.
• Different pages calling the same object 'Project' in one place and 'Workspace' in another, creating permanent user confusion about whether they're the same thing.

NielsenConsistency [principle] v1.0.0

Nielsen Heuristic 4: users should not have to wonder whether different words, situations, or actions mean the same thing; follow platform and industry conventions.

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

Attributed To

Jakob Nielsen, 1994

Applies To

• icon usage: same icon for same action across all screens
• color semantics: red = error/danger used uniformly, not decoratively
• keyboard shortcuts: matching OS conventions (Cmd+S, Ctrl+Z)
• terminology: using one term for one concept throughout all UI copy
• interaction patterns: identical controls behave identically everywhere
• component libraries: enforcing internal consistency via a design system

Counter Examples

• A SaaS product where the primary action button is blue in the dashboard, green in settings, and purple in onboarding — users lose confidence in which button is 'safe'.
• An app where Escape closes modals in some flows but does nothing in others — users can't form a reliable mental model.
• Different pages calling the same object 'Project' in one place and 'Workspace' in another, creating permanent user confusion about whether they're the same thing.

Sources

Examples

• Stripe's dashboard uses a consistent right-side panel drawer for every detail view — users learn this pattern once and apply it everywhere.
• Linear uses the same keyboard shortcut prefix schema (G for 'Go to', C for 'Create') throughout the product — internal consistency reduces the learning curve.
• Apple's Human Interface Guidelines enforce external consistency: swipe-from-left always navigates back, the Home indicator always dismisses to home — no app breaks this.

Source

• Jakob Nielsen, 'Heuristic Evaluation', in Nielsen & Mack (eds.), Usability Inspection Methods (1994)
• https://www.nngroup.com/articles/ten-usability-heuristics/