Jakob's law
People spend most of their time on other products, so they expect yours to behave like those.
Users arrive with expectations built from every other interface they use, and they apply those expectations to yours. Matching convention means the interface is understood without being learned. It is a heuristic drawn from usability practice rather than a measured effect, and its force depends on how strong the convention actually is.
How it shows up in software
Cart icons top right, logo links home, a red dot for unread, a hamburger for navigation on mobile. Following these costs nothing and saves the user learning. The tension is that a product differentiating on interaction has to break something, so the question is which conventions to keep, not whether to follow all of them.
Using it well
- Follow convention for anything peripheral to your value: auth, settings, navigation, search, account management.
- Break convention only where the new pattern is the product's actual advantage, and make the payoff visible within the first use.
- When you do break one, provide a bridge: a familiar path alongside the new one until the new one is learned.
- Verify the convention is real before following it. Conventions drift, and an old pattern copied from a decade-old competitor is just an old pattern.
Where it turns manipulative
- Copying a dark pattern: An interface built to get an outcome the user would reject if it were stated plainly. because competitors use it. The convention argument does not launder a pre-ticked box or a hidden cancel link.
- Using convention to justify never improving anything, so a bad pattern survives on the grounds that everyone has it.
- Mimicking the visual language of a trusted brand to borrow its credibility, which crosses from convention into deception.
Where you have seen it
Amazon
Cart top right, search bar across the top, logo linking home, the layout most commerce sites now follow.
Figma
Keeps standard file, edit and selection conventions from desktop design tools while breaking convention on multiplayer editing, which is the product's advantage.
Notion
Uses the familiar document editing model as its surface while the block structure underneath is the new idea.
What the research says
- Nielsen, 2000Contested
Formulated the law from usability consulting practice: users spend most of their time on other sites, so they prefer yours to work the same way.
A practitioner observation, not an experiment. It is repeated as a law without a study behind the name.
- Roth, Schmutz, Pauwels, Bargas-Avila and Opwis, 2010Mixed evidence
Participants held consistent expectations about where elements belong on common page types, and pages matching those expectations were navigated faster.
- Tuch, Presslaber, Stoecklin, Opwis and Bargas-Avila, 2012Mixed evidence
Prototypical page layouts received higher aesthetic ratings in very brief exposures, linking conventionality to first impressions.
Measures rated impressions of screenshots, not task performance in a real product.
Grades are a judgement about the evidence, not about how useful the idea is. Plenty of contested effects are still worth knowing, as long as you do not cite them as settled.