Why is @Google Drive asking now for an extension for offline access. What’s wrong or not available with just the Web Platform APIs?

"Make sure it works *only* on Chrome" is not a Web Platform API … yet.

There’s a lot of confusion about what the Chrome extension storage APIs do, in part because of confusing and out of date docs. I wouldn’t be surprised if this was just due to a misunderstanding... curious if @slightlylate or others know though?

There's a lot of legacy at work here. Extensions can get access to unlimited storage whereas we were pretty stingy for websites until recently. /cc @inexorabletash

My recollection is that it’s generally thought the extensions permissions would give you more storage (as the string “unlimited storage”) would suggest, but in fact it was persistence they affected, not quota. This area is mighty confusing though....

Yeah, that sounds right. We haven't had desktop PWA installability until recently so there wasn't really anything to hang the mobile durable-storage UI off of. I hope this will get better.

But isn’t Persistent Storage API the way to do it on Chrome without an extension?

Yes, but not meaningful on desktop without PWA installability...again, coming soon.

So, isn’t high-site engagement enough? or does that criteria work only on mobile?

it's all tied to engagement, but I'm not sure how you'd know you got high-enough engagement on desktop today. Will look at the code.

AFAIK the web platform still doesn't have filesystem APIs and IndexedDB file storage requires some rather unfortunate workarounds like splitting a large file into multiple blobs for storage and reassmebling them on read I may well be mistaken/out of date, though