How would HTML5 web databases be cleaned-up?

Question

I've started looking into HTML web database storage for some Chrome extension I'm working on, and it made me wonder - Who should be cleaning abandoned web databases? As opposed to desktop apps, there's no uninstaller for a web site. And as opposed to regular cookies, web databases can be much larger than just 4KB.

I can imagine some browsers or addons might give advanced users a way to clean up locally stored data, but I can't imagine my parents doing that. What will prevent web sites from clogging their hard drive once this feature is commonly used? Is there any way honest and responsible web sites can have their local data removed once they are not used anymore?

Answer 1

On the two websites and 4 apps I use html5 local storage in, I offer an option somewhere (off the About page, or in account settings, or a link at the bottom of the page) which gives you the ability to remove the local database and key-value pairs, as well as the option to opt-out of the site using it.

Answer 2

It'll be persistent, just like cookies. The difference with cookies is that you can store much more data and no expire date can be given.

Firefox has an option to clean those information automatically (Offline storage)