Making "files never leave your browser" verifiable with DevTools and CSP (opens in new tab)

"Files never leave your browser" is becoming standard copy for PDF tools, image editors, and document converters. But a trust claim and a verifiable fact are different things. Here's how to turn "zero upload" into something any user can audit in about two minutes, and how to enforce it at the browser level so it isn't just a promise. Step 1: Read the Network panel Open DevTools → Network, enable "Disable cache", reload. While processing a file, filter by "Fetch/XHR" and "Doc". A genuinely cli...