Using dark mode on your phone or computer screen dramatically reduces battery consumption.
Dark mode saves battery on OLED (organic light-emitting diode) displays because each pixel emits its own light; black pixels are switched off entirely, consuming zero power. LCD screens (common on older phones, laptops, desktop monitors) use a backlight illuminating all pixels uniformly; displaying black or white consumes nearly identical power because the backlight remains on regardless of image content. Smartphone manufacturers promoted dark mode when OLED adoption accelerated (Apple OLED iPhones, Samsung Galaxies), and the general 'dark mode saves battery' claim propagated into LCD contexts where it's false. Testing reveals battery savings of 5–15% on OLED devices with sustained dark-mode use (averaging content across sessions), a meaningful but modest improvement. Marketing conflated OLED optimization with universal advantage. Understanding display technology reveals the underlying difference: LCD is backlight-based (content-agnostic power draw), OLED is pixel-emissive (content-dependent). Blanket 'use dark mode' advice persists despite being context-dependent, an example of technology guidance becoming oversimplified once removed from engineering detail.