I wrote this post (and recorded the DevTools demo) to highlight a behavior many users overlook: AI chat interfaces run JavaScript that captures your keystrokes in real-time. Even if you paste sensitive data and delete it before clicking send, background telemetry or auto-save requests have often already transmitted it to the server.
To solve this, I built ChatWall. It’s a browser extension that intercepts this process using a secure overlay.
Instead of typing into the chat's native input field (where host scripts can read it), you type into our isolated extension context. It detects and replaces PII (names, emails, IBANs) with neutral tokens locally on your machine. Only the already-masked text is ever passed to the host page.
100% Local: All processing runs in your browser. We have no backend.
Open Source: The core masking logic is on GitHub so you can audit exactly what the extension is doing.