A test page that tries to store things in various back ends (cookies, localStorage, IndexedDB) to help you assess if your Developer Tools let you inspect and edit the data comfortably.
Access index.html using a secure protocol, or visiting this site. It'll remove previous test data (if present) and install new test data. Open your developer tools and look at the storage tool and see what works and what doesn't.
The index.html page also contains an analysis of each area and the current results. These are manual and are not automatically updated.