What is the storage limit? Would be nice to offer some kind of helper function to return that. For instance, I want to store a base64 encoded image. I believe there is a 10MB limit imposed by Chrome on local storage (or something similar). Bypassing that restriction locally would be great. Could be a nice feature of ImmortalDB.

That won't fit in cookie space... this is really for redundant controls for session/access tokens etc... anything large like that you're better off using caching and a service worker to handle repeated requests. Also, cookies are sent with every request to the server, and I don't think you'd want the user sending 10MB to your server for every request.

Also, if you are storing larger strings in local/sessionStorage, websql or indexdb, you should use lz-string[1] to try to minimize storage impact.

Aside: if you want something with a nicer interface for underlying storage you may want to look at pouchdb[2], which has a localized couch interface and supports remote synching to coudchdb, which is pretty nice.

[1] https://github.com/pieroxy/lz-string [2] https://pouchdb.com/