The key is the file and folder picker methods (showOpenFilePicker() etc), allowing the web app to interact with existing files and folders on the device. OPFS does not allow that, as it's internal storage in the browser, like IndexedDB.
As for writing, you don't get unlimited unchecked writes the way that Chrome's proposed Filesystem Access API grants you, but you can trigger "checked" writes (that show a file save dialog) using `<a/>` elements with the `download` attribute. This is arguably a better user experience, because it keeps the user in the loop, giving them the opportunity to veto (or rename/relocate) the written file—which will be difficult or impossible to do if the Chrome team's proposed API became standard.
Overall, the File System Access proposal is a bad one that gets the developer vs user prioritization wrong (favoring the convenience and satisfaction of the former over preserving control for the latter), and I hope it doesn't become either a de facto or a de jure fixture of the Web platform soon. Here's to hoping for a future post to the Chrome Developers blog announcing that this is yet another experimental API of theirs that they have decided is going to be sunset in some future release.
This is access to some controlled contents that happen to come from the filesystem, with interaction explicitly initiated by the user every time. It gives the browser no access to the structure of the filesystem, no way to navigate it, and crucially no way to transparently read or write anything.
This is good isolation, I'd prefer it to be this way. OFS also gives equally good isolation, I'm fine with that.
Sharing between OFS and the rest of the user's file system should be possible, but only explicitly, a la iOS, Android, and the file upload / download dialog.
> This is not access to the filesystem.
Wrong. I know what "this" is, thanks, and it is access to the filesystem. That's because "this" here—in the subthread you have just posted to—refers to Chrome's experimental implementation of the larger proposal (which is literally called "File System Access API"), not the limited subset described by the submission as having just gotten enabed in Firefox.
While Google's new API definitely is.
It's the `download` attribute, but yeah, I understand the significance of those words. I wrote them.
Your replies in this thread, on the other hand, are confusing at best. What are you actually trying to communicate?
Why is arbitrary access to a whole folder needed? Cool, yes. Dangerous? Very.
Making users repeatedly upload and download the same file to work with it is clunky.
People having been doing that with Word and other local word processors using (SMB) file shares for decades. There's nothing special about web browsers that's causing it.
And if they’re not the sole persistence mechanism, if downloads are just an export option separate from a ‘normal’ save, like you see in most web apps, then the 99.9% of users who don’t constantly export all their documents will have to deal with the consequences of the normal persistence mechanism. That is probably cloud storage, with associated centralization, privacy, and cost concerns, though it could also be browser-local temporary storage (cookies / localStorage / IndexedDB / origin-private file system), with reliability and portability concerns.