Poor Man's Back End-as-a-Service (BaaS), Similar to Firebase/Supabase/Pocketbase

Do we still need a back-end, now that Chrome supports the File System Access API on both desktop and mobile?

I have started writing web apps that simply store the user data as a file, and I am very pleased with this approach.

It works perfectly for Desktop and Android.

iOS does not allow for real Chrome everywhere (only in Europe, I think), so I also offer to store the data in the "Origin private file system" which all browsers support. Fortunately it has the same API, so implementing it was no additional work. Only downside is that it cannot put files in a user selected directory. So in that mode, I support a backup via an old-fashioned download link.

This way, users do not have to put their data into the cloud. It all stays on their own device.

What about those of us who use multiple devices, or multiple browsers? I've been using local storage for years and it's definitely hampering adoption, especially for multiplayer.

One approach might be to save the file to a shared drive like Google Drive?

Not sure I trust Dropbox to merge data. What happens when I want to migrate my data structures to a new schema?

As far as I know, Dropbox does not merge data.

I never tried it, but from the descriptions I have read, Dropbox detects conflicting file saves (if you save on two devices while they are offline) and stores them as "conflicting copies". So the user can handle the conflict.

As a developer, you would do this in the application. "Hey, you are trying to save your data but the data on disk is newer than when you loaded it ... Here are the differences and your options how to merge.".