What is Jakob's law in UX design?
Jakob's law was formulated by Jakob Nielsen and states that users spend most of their time using products other than yours. This means they arrive at your interface with established mental model built from years of experience with other products. They expect your interface to work the way those other products work. When it does, interactions feel intuitive. When it doesn't, users face unnecessary cognitive load as they work to reconcile their expectations with the reality of your product.
Why is Jakob's law important for UX design?
Jakob's law provides a principled basis for following established conventions rather than creating novel interface patterns for their own sake. Innovation in interface design carries a real cost: every time a designer replaces a familiar pattern with something new, they are asking users to unlearn existing behavior and learn new behavior. That cost is often not justified by the benefit of novelty. Jakob's law is the reason why hamburger menus appear in the top left on mobile, why shopping carts use a bag or cart icon, and why links are underlined.
What are examples of Jakob's law in interface design?
Users expect the logo in the top left of a website to link to the homepage because this convention is nearly universal. Users expect the back button to undo the previous navigation action because every browser and mobile OS works this way. Users expect a settings icon to look like a gear because this metaphor has been established across thousands of products. Violating these expectations requires users to discover and adapt to something new, which creates friction and increases the probability of error.
When should you follow conventions and when should you break them?
Follow conventions by default, especially for navigation, labeling, and interaction patterns that users encounter across many products. Break conventions only when there is a clear and specific reason why the convention fails for your particular users and context, and when you are prepared to invest in helping users learn the new pattern. The default assumption should always be that the convention exists because it works, and that breaking it requires justification.