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Users spend most of their time on other sites and prefer yours to work the same way.
stellae.design
Users spend most of their time on other sites and apps, so they expect yours to work the same way. Jakob's Law urges designers to leverage existing mental models rather than forcing users to learn new patterns. Innovation should be intentional, not accidental.
Users spend most of their time on other sites. This means that users prefer your site to work the same way as all the other sites they already know.
Task: Add an item to your cart in two different store layouts. We'll time you.
Users expect "Add to Cart" to be prominent and immediately visible. Familiar patterns reduce friction.
E-commerce with familiar layout patterns
Cart top-right, search prominent, categories on left — standard and intuitive
E-commerce with unconventional navigation
Cart hidden in a side panel, search buried in footer, confusing layout
The mechanism behind Jakob's Law is mental models — the internal representations people build from past experience. When an interface matches existing mental models, users can predict outcomes and act confidently. When it doesn't, they hesitate, make errors, and may abandon the product entirely. This is a central concept in HCI research and is well-documented in Nielsen Norman Group's guidance on mental models.
Nearly all successful e-commerce sites place the product image on the left, description and price on the right, and 'Add to Cart' button prominently below the price. Users have been trained by Amazon, Shopify stores, and countless others to expect this layout. Deviating from it forces users to re-learn a pattern they've internalized from thousands of prior shopping experiences.
The three-line hamburger icon has become a universal signifier for hidden navigation on mobile devices. While it was controversial when first introduced, it now carries such strong learned expectations that using a different icon for the same function would confuse most users. Jakob's Law argues for using it because that's where users spend most of their time.
Snapchat's 2018 redesign dramatically reorganized the app's navigation, mixing friends' content with publisher content and moving core features to unexpected locations. Over a million users signed a petition against the change, and the company lost significant market share. The redesign violated Jakob's Law by breaking deeply ingrained usage patterns built over years.
Users expect login forms to contain an email/username field, a password field, and a submit button — in that order. They expect a 'Forgot password' link near the password field and a 'Sign up' link nearby. This convention is so strong that even minor reordering (password before email) creates measurable friction and support requests.
• Treating Jakob's Law as 'copy competitors' — the real principle is 'match user expectations within the mental model of the domain.'
• Overstandardising, which can erase meaningful differentiation and freeze broken conventions in place.
• Ignoring that different user groups (radiologists vs. children) have completely different dominant mental models.
| Check | Good Pattern | How to Test |
|---|---|---|
| Convention audit | Core interaction patterns (navigation, forms, CTAs) align with the conventions established by the top 5 products your users also use. | Survey your users about which other products they use frequently. Map your key interaction patterns against those products and identify deviations. |
| Component pattern alignment | UI components (dropdowns, modals, tabs, date pickers) behave the way users expect from their experience with other products and the operating system. | Run a usability test where users interact with each component type. Track whether their first-attempt interaction succeeds — failure indicates a violated convention. |
| Innovation justification | Any deliberate departure from convention is documented with user research evidence showing that the new pattern performs measurably better. | For each non-standard pattern in the interface, verify that an A/B test or usability study exists showing superior performance over the conventional alternative. |
Break convention when (1) the current convention demonstrably fails users, (2) your context is specialised enough that users already expect training, or (3) you can introduce novelty gradually with strong signposting and reversibility. The constraint is not 'never break' — it is 'don't break silently, suddenly, and everywhere.'
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