1. How to turn on dark mode on Android
On most Android phones the process is very simple: go to Settings → Display and look for the Dark mode option (on some manufacturers it may be called Dark theme). Once turned on, the system and many apps switch to dark backgrounds with light text immediately.
From that same screen there's usually a section to schedule it automatically, so it turns on only at nightfall or during the hours you choose, without having to remember to switch it every day.
2. How to turn on dark mode on iPhone
On iPhone the process is similar: go to Settings → Display & Brightness and choose the Dark option under appearance. The change applies instantly across the whole system and in apps that support it.
Right below you'll find the Automatic option, which lets your iPhone switch between light and dark based on the time of day or following the sunrise and sunset at your location, without you having to touch anything else.
3. The real benefits of dark mode
The most noticeable benefit is visual: in low-light environments, looking at a screen with a dark background is less bothersome and reduces eye strain, especially if you use your phone at night before going to sleep.
As for battery, the savings are real but depend on the type of screen. On OLED or AMOLED screens, which most current phones have, black pixels turn off individually and use less power, so dark mode can genuinely extend battery life. On older LCD screens the backlight works the same whether the background is light or dark, so the savings are much smaller or almost nonexistent.
4. Why some apps don't change color
Turning on the system's dark mode doesn't guarantee every app will adapt. Many follow the general setting without any issue, but others have their own theme switch inside their internal settings, independent of the system. If you notice a specific app still showing in light mode, check its appearance settings within the app itself.