Jakob's Law

The law

Users spend most of their time on other sites, so they expect yours to work the way those sites already do.

The habits a person brings to your product were formed somewhere else. Every place where your interface breaks those habits is a place where they have to stop and learn.

Where it comes from

Jakob Nielsen stated the law in his Alertbox column End of Web Design, published on 22 July 2000. His argument was about the web of the time: any single site is a small part of a person's day online, so the conventions set by all the other sites outweigh anything one site can teach. He used it to argue that web design was becoming a matter of following established conventions rather than inventing new ones.

It is an observation about how people learn interfaces, not the result of a single experiment. It rests on a well-studied idea from psychology: people build mental models from experience and use them to predict how a new system will behave. Nielsen's contribution was to point out where most of that experience comes from.

What it means for an interface

• Conventions are a resource. A logo that links home, a search field at the top, a cart icon in the top right, underlined links: people already know these. Using them costs your users nothing.
• Novelty has a price. A new interaction may be better in isolation and still lose, because people have to notice it, understand it and remember it. Spend that price only where the gain is large and you can show it.
• The relevant convention is the one your users know. For a banking app it is other banking apps and the platform's own controls; for an internal tool it may be the spreadsheet it replaces.
• Redesigns follow the same rule. Your own previous version is one of the "other sites" your existing users know. Change it in steps, and keep familiar paths working while people adjust.

Examples

Checkout. People expect a cart summary, a clear total, and a single primary button to continue. A checkout that hides the total until the last step, or labels the main button with an unusual word, makes people hesitate at the moment that matters most.

Navigation. Breadcrumbs, a site logo that returns home, and a main menu at the top or left are learned on thousands of sites. A product that moves its main navigation into an unlabeled gesture or an unusual corner asks every new user to find it again.

Platform controls. On mobile, people expect the system's own back gesture, share sheet and date picker. A custom date picker that looks different from the platform's has to be learned from scratch, even if it looks better.

Where it is misapplied

• As a ban on change. The law describes a cost, not a rule against new ideas. New patterns do become conventions once enough products adopt them; pull-to-refresh is one example. Measure the gain before paying the cost.
• Copying the wrong product. "Users know Amazon" is only true if your users are Amazon's users. The conventions that count are the ones your actual audience uses every day.
• Copying surface without behavior. A control that looks like a familiar one but works differently is worse than an unfamiliar one, because it breaks the prediction it invites.
• Treating it as proof. It is a strong default, not evidence about your product. When a convention and your usability test results disagree, the test wins.

Checklist

• The primary controls look and sit where comparable products put them.
• Every place where the design departs from a convention has a stated reason and a measured benefit.
• Familiar-looking elements behave the way their look promises.
• The platform's own controls are used unless there is a tested reason not to.
• A redesign keeps the old paths working while existing users adjust.

Related

• Hick's Law: familiar options are faster to choose between.
• Miller's Law: conventions free up limited working memory for the task.
• Serial position effect: where people expect to find the items they use most.
• Patterns: Breadcrumb, Pagination.