Cognitive load is the amount of mental processing power required to use a website interface. The human brain can hold roughly seven (plus or minus two) information units in working memory at once, for about 20 seconds. When a website demands more mental effort than that capacity allows, users struggle with tasks, miss details, and experience overwhelm.
Three types of cognitive load apply to web design. Intrinsic load is the inherent difficulty of absorbing new information; it cannot be eliminated because it is tied to the complexity of the content itself. Extraneous load is mental processing caused by poor design: unnecessary distractions, visual clutter, confusing elements, and inconsistent patterns. Designers can and should minimize this type. Germane load is the mental effort a user willingly invests in understanding and completing a task; the goal is to maximize this type by making the productive work feel natural. Design strategies that reduce extraneous load include eliminating visual clutter, building on existing mental models, offloading tasks to the interface, using consistent patterns, chunking content into digestible groups, and optimizing response times. High cognitive load slows information absorption, increases error rates, and reduces satisfaction.