Jakob's Law¶

Status: emerging
Last updated: 2026-06-02
Sources: Lawsofux.Pdf
Tags: [ux-design, design-principles, heuristics, jakobs-law, mental-models, conventions, usability]

Summary¶

Jakob's law holds that users spend most of their time on sites other than yours, so they expect — and prefer — your product to work the way the others they already know do (Yablonski, 2024). Yablonski attributes the law to usability expert Jakob Nielsen (2000) and frames it through mental models: people carry expectations built from prior experience, and an interface that matches those expectations feels intuitive while one that violates them causes friction. The practical advice is to follow established conventions and, when change is necessary, to let users opt in gradually rather than forcing an abrupt redesign.

Body¶

Context¶

Yablonski (2024), in the opening chapter of Laws of UX, applies Jakob Nielsen's observation about cross-site user expectations to design practice. The chapter states the law, grounds it in the concept of mental models, and uses redesign case studies to show the cost of violating user expectations. Within this knowledge base the article connects to Usability And User Experience (conventions and user-centred design) and to the mental-model material that also underlies Situation Awareness; it is one of the experience-and-expectation laws in Laws Of Ux.

Key Points¶

Yablonski states the law, attributed to Jakob Nielsen (2000), as: users spend most of their time on other sites and prefer your site to work the same way as all the other sites they already know (PDF pp. 23–34, orig. pp. 3–14). He explains it through mental models — the knowledge a person carries from past experience and applies to new systems — so that good design aligns with users' existing models and a mismatch produces frustration.

The chapter's design guidance concerns conventions and change management. Following familiar patterns lets users transfer existing knowledge to a new product; departing from them imposes a relearning cost. Yablonski illustrates the risk with the 2018 Snapchat redesign backlash and recommends mitigating disruptive change by letting users opt in to a redesign gradually, citing products such as Google Calendar and YouTube that offered a transition period (PDF pp. 23–34, orig. pp. 3–14). The chapter also addresses the obvious tension — whether the law argues that every product should look the same — and answers that it argues for honouring established expectations, not for sameness.

Conclusion¶

Yablonski (2024) concludes that Jakob's law is a case for designing with users' existing mental models rather than against them: convention is a usability asset, and innovation should be introduced in ways that let users carry over what they already know. Abrupt, mandatory change is the failure mode the law warns against.

References¶

Nielsen, J. (2000) End of Web Design. Nielsen Norman Group. Available at: https://www.nngroup.com/articles/end-of-web-design/ (Accessed: 2 June 2026). To be validated.

Yablonski, J. (2024) Laws of UX: Using Psychology to Design Better Products & Services. 2nd edn. Sebastopol, CA: O'Reilly Media. yablonski2024lawsux

Open Questions¶

When does following convention (Jakob's law) conflict with genuine product innovation, and how should designers decide which to favour?
How do cross-product mental models form and transfer across platforms (web, mobile, spatial), and how stable are they over time?