I filed bug 630858 a long time ago for a piece of this puzzle, but given the unification in bug 767944, we probably should do this as a unified management interface. When implementing Tahoe Data Manager - https://addons.mozilla.org/addon/data-manager/ - I could make use of the interfaces we have for our Cookie, Password, etc. Manager UIs to list all the stored pieces of data (in my case by domain), manage (clear/remove) them, and observe modifications (added/removed/changed) to update the UI when already open. See nsICookieManager2, nsILoginManager, etc. for those. Cookies, passwords, content prefs, permissions, even saved form data (though not site/domain-specific) have good interfaces for that kind of management and view, but (web) storages don't really have that, probably because we didn't design sophisticated management UI in Firefox itself. Because of that, I currently have quite hacky and not always completely working code in Tahoe Data Manager (which is also shipped as in integrated part of the SeaMonkey suite). We should create such an interface with the new unified storage manager so that add-ons can do such management UI reasonably. With the growth of HTML5 and usage of those storages, demand for some better Ui might even come up for in-product. IMHO, this should entail: * Listing storages with site, type and size (enumerator) * Ability to remove a certain type of storage for a certain site (i.e. one entry of above list) * Observer notifications for adding/removing/changing storages.