BrowserFS has a few different APIs integrated. Not the lightest library though.

https://github.com/jvilk/BrowserFS/blob/master/README.md

I would also love such a library. I currently follow the same pattern of making web apps that only use local storage so I don’t have access to user data, but would like to allow users to easily use their existing cloud services for persistence.

Check out https://kloudless.com! (Disclaimer: I'm a co-founder)

Here's our open source file picker: https://github.com/kloudless/file-explorer/ (the server-side is closed source and requires a paid subscription beyond a point)

Maybe something like https://kloudless.com/ haven't used them though

Only other option I could find is https://github.com/rclone/rclone but it's a commandline tool

The remoteStorage reference client can also sync with Google Drive and Dropbox:

https://remotestoragejs.readthedocs.io/en/latest/getting-sta...