Why does a site even need a light/dark toggle, when you can just use prefers-color-scheme in CSS, and the user can select that in their browser settings?

(Also, technically, alternative stylesheets can be defined in HTML, except every browser except Firefox removed it: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...)

Because being able to switch from light to dark mode by clicking a single button is a useful feature, and while it would be nice if operating systems provided this out of the box, many (e.g., Windows) do not.

> Why does a site even need a light/dark toggle, when you can just use prefers-color-scheme in CSS, and the user can select that in their browser settings?

Good question, especially since the Ruby site already does this by default. Perhaps the argument is that one of the two color schemes may be designed so poorly that the user may want to manually switch to the other one.

Because as a user, I want to change the light/dark of your site, not every set, and not my OS. If you don't have a toggle, you are making assumptions that aren't accurate.