Dark Pattern

Dark pattern names an interface designed on purpose to make the user do something they didn't intend — subscribe, overspend, share data — by exploiting the same perceptual and cognitive shortcuts that good design usually serves the user with. The term was coined by UX researcher Harry Brignull in 2010, and its defining feature isn't bad design, it's effective design pointed at the wrong goal: a dark pattern typically works exactly as intended, which is what makes it worse than a mere usability failure.

The catalog is by now well documented and mostly reduces to a handful of moves. "Confirmshaming" guilt-trips the decline option ("No thanks, I don't want to save money"). A "roach motel" makes signing up one click and canceling a multi-step phone call. Drip pricing reveals fees only at the final step, after switching costs have risen. Forced continuity auto-renews a trial without a clear reminder. Most of these exploit Hick's Law and Fitts's Law in reverse — deliberately raising the decision cost or the physical reach cost of the option that serves the user, rather than lowering it.

Regulation has started catching up to the vocabulary: the EU's Digital Services Act and California's privacy law both name deceptive interface design directly rather than leaving it to general consumer-protection statutes, which is a sign the pattern moved from "ethics essay topic" to "compliance risk" in about a decade.

The distinction that matters in practice is intent and asymmetry, not mere persuasion — a well-designed default or a genuinely limited-time discount isn't a dark pattern just because it changes behavior. It becomes one when the interface makes the business-favoring path measurably easier to complete and the user-favoring path measurably harder, especially by hiding, delaying, or obscuring information the user would need to decide well.