IconVault's IndexedDB Explorer lets you inspect the IndexedDB databases stored by websites in your browser: list object stores, page through records (25 per page, up to 500 reads), and view keys, values and indexes. You can add, edit and delete records, and import or export JSON for backup or migration.

It runs entirely in your browser with no signup and is free. Honest notes: for privacy and security, browsers only expose this origin's databases, so you see IconVault's own storage here, not other sites'; and edits write straight to the live database, so export a backup before changing production data.