I explained hashes to my daughter once, and she got it in a single sentence: "Oh, so you store the cookie, not the recipe." Yeah — it's kind of like that.
A hash is a one-way math trick. You feed in some text — a sentence, a whole document, anything — and out comes a short, fixed-length string of letters and numbers. We use one called sha256. The same text always produces the same hash, so we can tell two things apart or confirm that something hasn't changed. But it only runs one way: from the hash, there is no path back to your original words. The recipe never comes out of the cookie.
Change a single comma and the hash changes completely — it doesn't drift a little, it turns into something entirely different. That's what makes it useful for showing a file is untouched.
Here's why that matters for your privacy: the patterns that truly identify you as a writer never leave your machine. What the app sends us about your writing is a sha256 hash and an opaque document id — nothing else. So if a hacker grabbed that database, they'd have a pile of cookies and no recipes — 100% useless to them. There's nothing there to steal that could be turned back into you or your writing.
Two things you type on this website do reach us, because you chose to send them: the email address you enter to join the beta, and the text of a problem report if you file one. Neither is your writing.