I created this extension as I was concerned about the number of old accounts linked with different email addresses I have. I became more concerned about privacy and my data but couldn't find an easy way to check what emails are account related.
You export your emails as an MBOX file (Google Takeout makes this easy), load it into the extension (the video doesn't show the window for choosing the file), and it scans locally on your device to find every service you've signed up for. No data leaves your computer. The extension requires zero permissions and makes zero network calls.
It also flags active subscriptions (which are also easy to forget about) and gives you direct links to account deletion pages (using a subset of an open data project called justdeleteme (no affiliation)), so you can more easily do something about it.
Built with plain JS and no framework; all the parsing happens in a Web Worker so even large mailboxes don't freeze the browser.
It's called find my accounts and it's free on the Chrome Web Store. Appreciate any feedback.
https://chromewebstore.google.com/detail/find-my-accounts/apeccjnoepacandnpapofclblfkokiif