Dark mode toggles: two states are enough • Lea Verou

Lea Verou argues that dark mode toggles should have only two states rather than three (Light, Dark, System). The core argument is that users only seek out theme toggles when something is wrong — not to preemptively express intent — making the 'System' state irrelevant at the moment of interaction. Tri-state toggles expose the underlying data model rather than aligning with actual user goals, adding cognitive load and UI friction for an extremely rare use case. A well-implemented two-state toggle can still represent all three underlying states: the first click overrides to the opposite of the current resolved value, and the second click removes the override and returns to system default. Common mistakes include storing a value that matches the system preference (silently pinning the theme) or removing overrides when the OS preference changes. Exceptions where tri-state controls are appropriate include dedicated settings panels and sites that implement meaningfully different color schemes depending on the OS setting.