IndexedDB is often recommended for storing large amount of data in WebExtensions (or Chrome Extension). "unlimitedStorage"
seems to apply to both IDB and Storage.
In case of non-tabular text data where the indexed searches are not needed, what is the benefit of using IndexedDB over Storage?
They both use object based architecture and there is a great performance overhead in case of IDB.
I tested parsing and saving 4mb data to storage which took less than 1 second while in case of IDB it hung the browser for minutes and I had to forcefully shut it down.
Reference: Chrome extension store large amounts of data
Only WebSQL, IndexedDB, chrome.storage.local and HTML5 File System (sandboxed file system) can grow past 5MB limit via "unlimitedStorage" permission.
manifest.json: "permissions": ["unlimitedStorage"]
Provides an unlimited quota for storing HTML5 client-side data, such as databases and local storage files. Without this permission, the extension or app is limited to 5 MB of local storage.