Interaction Cost

Interaction Cost refers to the mental, physical, or temporal effort required by users to complete a task or action within a system. The higher the interaction cost, the more likely users are to abandon tasks or experience frustration. Reducing interaction cost is a key principle in user-centered design, and it can be achieved by simplifying workflows, reducing steps, and providing clear instructions.

Interaction cost is the invisible tax your product charges users for every action they take. Multiply that tax across a daily workflow used 50 times, and even small friction compounds into significant frustration. For B2B SaaS tools where users perform repetitive tasks — logging calls, updating status fields, reviewing items — minimizing interaction cost per action is often more impactful than adding new features, because it directly affects how much users enjoy using the product daily.

Linear obsessively minimizes interaction cost for developers — keyboard shortcuts for every action, instant search to navigate anywhere, and single-click status updates — because their core users perform these actions dozens of times per day and every unnecessary click compounds into real frustration.