If it's not hard, shouldn't that ideal be towards the handful of browser vendors rather than the thousands/millions of website owners? I agree, if you're going out of your way to provide different stylesheets, provide a toggle, otherwise it's kind of a wasted effort anyway. However, my point of argument is the ideals. The idea someone SHOULD provide something. That SHOULD should be towards browser vendors, not website owners.
>And that's totally fine! If you don't have separate color schemes, it would make no sense to include a toggle. But if you have separate color schemes, add a toggle.
I don't think it's fine in your scenario, and the current state of things. If we require websites to individually provide their own toggles, how will the user know a toggle is even available or not? It creates an inconsistent UX where some websites have toggles and others don't. How many Hacker News visitors wasted time looking for a dark mode toggle that doesn't exist?
Which is why having it at the browser-level is necessary. Not to mention storing state, one of my pet peeves is using Incognito and losing my preferences.
It's kind of funny to me because Alternative Stylesheets solved this problem decades ago. Just like how Firefox used to have an RSS icon so we knew a website had RSS without needing to look for it. All of this stuff has been delegated to web extensions, which is barely supported on mobile. So we all need to plaster our websites with what we do and don't support and hope users find them.