Imagine browsers offering synced
window.localStorage, with an in-browser UI for whether you’re logged in to a site. It would be like iCloud for the web - syncing data via your browser sync password, obviating the need to create a new account for every application that wants to store data, as you’re already logged in to iCloud.
Conceptually, the user could whitelist sites to allow this; the browser would integrate the whitelist into the log-in UI. This would let the browser keep you logged in forever, fixing the terrible short cookie expiry timelines that browsers enforce now to limit tracking. The in-browser UI would be unspoofable (like eg the Firefox extension installation UI), and it would be impossible to phish the credentials (sort of – attackers could phish the credentials for the sync service, but not individual websites that use it).
localStorage for user data. Today, lots of apps basically use a server just for hosting user data since browser storage is so unreliable – those apps could be ported to the web (many automatically with webasm) and live ~forever without requiring hosting costs and security updates. Basically any app designed to run on a desktop operating system and save data to the hard drive could be ported – MS Paint, Text Edit.app, a full Linux virtual machine with a persistent filesystem via v86.
Details to work out: Do you allow sharing data between websites? iCloud doesn’t, which is annoying, but the implementation is simpler. The best implementations would be end-to-end encrypted. Ideally, you’d be able to mix and match storage providers between different browsers, like using Firefox on Windows to sync with Safari on an iPad.
A browser extension could do this, but then sites would have to support it specifically. Might be useful as a proof of concept though. I wonder if there are enough primitives in Safari extensions to implement it today?