There is a very real problem with this extension that will upset people that use it. It’s using the window.localStorage object that will possibly be cleared out when the browser history gets erased. It asks for the storage permission in the manifest but does nothing with it. To the op, use chrome.localstorage() for any read and write operations(edit note that this is async)... that protects against clearing the history. If you plan on storing images you can just request the unlimitedStorage permission to get a full indexdb instance with the same simple api that is simple to use. (not sure if this perm is valid on chrome)