Type something. Watch it lock.
Most privacy pages describe the encryption. This one runs it. Everything below happens in your browser, on whatever you type, using the same code that runs when you save a journal entry.
Shown, not masked. It is a demo passphrase for a demo key, and hiding it would only make the page harder to follow.
The encryption below runs here, in this tab. It makes no network request, stores nothing, and the key it generates is gone the moment you leave. Open your network tab and watch. The page around it loads the same cookieless analytics as the rest of the site, and that is the whole inventory.
What this doesn't prove. Which matters more.
What you just watched proves the algorithm and the key path. It proves the ciphertext is real, the nonce changes, and a wrong passphrase is refused rather than fumbled. It proves all of that about the machine it ran on, which is yours.
It cannot tell you what our server does with what it receives. A page that runs in your browser can only vouch for your browser. Anyone claiming otherwise is selling you a demo.
Two things would settle the other half. The first you can do right now: open your developer tools, network tab, and save a journal entry in the app. Read the request body. It carries base64 and an IV, and the words you wrote are not in it, in any form.
The second is reading the code that this page just ran. It is not open yet. That is a real gap and not one this page can close for you, so it is written down here rather than left out. When the source opens, this paragraph changes.
Until then you have checked one half properly and are taking the other on trust. That is worth saying plainly, because a page that implied otherwise would be the first thing on this site you had reason to doubt.
The architecture in full, including the parts this page cannot demonstrate, is on the deep overview. The short version is the privacy page.
A lock you watched close is a different thing from a lock you were told about.