The Internet is not asleep. This means that you can look at a brightly lit display at any time of day, which may affect your sleep and your eyesight. Turn off the lights by turning on dark mode in your browser.
Many popular mobile apps offer darker color schemes, but on the Web, the color scheme of each site is determined by the site's developer. Nevertheless, you can simplify browsing for the eyes by changing the color of the menu pages or playing with certain experimental features. That's how it's done in Chrome, Firefox, Safari and Edge.