The principle that users spend most of their time using products other than yours, so they arrive with expectations shaped by those experiences. Designs that conform to established conventions feel intuitive; those that break them force users to learn new patterns, increasing cognitive load and the chance of error.
Common contexts
- Pushing back on a stakeholder request to move the primary navigation to the bottom of a desktop interface
- Evaluating a proposed custom date picker against the native OS picker for a mobile booking flow
- Defending a conventional checkout pattern against a brand team that wants a 'unique' multi-step experience
Use when
Invoke Jakob's Law when a proposed design departs from platform or category conventions without a measurable benefit — the burden of proof should be on differentiation, not conformity.
Avoid when
Don't use it to shut down all innovation — conventions become outdated, and sometimes a product's competitive advantage lives precisely in doing something familiar in a meaningfully better way.
Jakob's Law is most useful not as a design rule but as a challenge to stakeholders: what specific user benefit justifies the learning cost of breaking this convention?
Real-world examples
- Every major e-commerce site places the shopping cart icon in the upper-right corner — a convention so strong that deviating from it, as early Etsy A/B tests showed, measurably increases cart abandonment.
- Spotify's desktop app on launch day adopted an iTunes-style library sidebar, deliberately leveraging the mental models 500 million iTunes users already had rather than inventing a new paradigm.
- Google Search maintains its 'ten blue links' format as the baseline precisely because users have spent decades building mental models around it; radical UI departures consistently reduce CTR in experiments.