If your intention is to let the user choose between styles the best way would be Alternate Stylesheets: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/... . Sadly Google can't be bothered to implement "legacy" standards (=standards not invented at Google).

If your intention is to adopt your styles slightly to user preferences then there are media queries.

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Telaneo 5 days ago | parent [-]

Alternate stylesheets don't persist (at least in Firefox), which is really annoying.

Media queries are really nice though. Being able to provide a night mode alternative without even asking the user, assuming they've set the OS to their preference, is really seamless.

	▲	1718627440 5 days ago \| parent [-]
		> Alternate stylesheets don't persist (at least in Firefox), which is really annoying. Yes, I also think they should. What I wondered, is this behaviour prescribed somewhere? Even if it were, form content is retained even across randomly typing in a different URL and navigating back, form submission and even across real crashes just seconds after I typed the letter. This is really nice and I don't think it is mandated. This is the stuff User Agents should be compete with, not ways to get data from the User to a surveillance company. > Being able to provide a night mode alternative without even asking the user, assuming they've set the OS to their preference, is really seamless. Yes, that's nice and how every thing in a UI should be. It helps both the programmer and the user in efficient and controllable usage.