User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0 Build ID: 20161208153507 Expected results: The ability to save, load, or pick the local disk is essential for many addons to work. For example, *ScrapBook* saves data to a specific location in the disk and loads rdf or other data from the local disk. *MAF* saves the web page as a zip (.maff) to the disk, extracts .maff to a spcific path of the local disk. *WiredMaker* saves/loads data to/from the local disk as well. Additionally, we probably need the ability to manipulate zips, the ability to connect, read and write a sqlite, an RDF file, etc. There is probably a security concern for accessing the local disk, we can do something like Chrome app, which allows the user to grant access permission for a specific local directory via an explicit prompt.

You covered a lot of ground here, duping this to the main filesystem access bug. Regarding specific file formats, you already have access to IndexedDB in webextensions. Without a very compelling reason, I don't think we would add sqlite in addition. As for zip and rdf, those can be implemented in javascript. Again, we want to avoid unnecessarily adding things to the webextensions API surface that can already be done in another way. If there's some sort of performance concern, we can discuss that but please be specific about why the existing means won't work.

What is the API for IndexDB in WebExtensions?

(In reply to Danny Lin from comment #2) > What is the API for IndexDB in WebExtensions? It isn't any different than for regular web content. You can just use it from your background page/script as you would from a regular web page.