I wish the Safari content blocking API allowed cookies to be blocked. I'd block cookies for 99% of sites I visit, allowing them only for the handful of sites to which I login. I'd suggest Safari could even make cookies require getting user permission, the same way location access needs to be granted. "Allow, allow for 24 hours, deny." It could default deny except for sites to which it has a saved password which could…
It already does that! 1Blocker lets you specify a list of websites for which cookies won't be sent in the request headers. So I suppose the API indeed supports this feature.
https://developer.apple.com/documentation/safariservices/cre...
https://kb.adguard.com/en/general/how-to-create-your-own-ad-...
(I switched from 1Blocker to Adguard because 1Blocker wasn't working very well for me.)