The free web product is a browser-based PDF workspace. The important part is where file bytes go: they stay inside the browser runtime for core local operations. Cloud API and AI features are a separate authenticated product surface.
Your browser downloads the website code, styles, icons, and assets from the host. That is normal web delivery and not the same thing as uploading your document.
When you choose a file, the browser gives the page a local File object. Core tools read and transform that file in browser memory or a browser worker.
The output is turned into a downloadable blob on the client. There is no core processing endpoint that receives the document just to send it back.
The visible interface handles uploads, previews, and interactions. A browser Web Worker handles heavier PDF byte operations so the UI remains responsive. Both still run on the user’s device.
Local processing protects against the app uploading your file contents in the free tool flows. It does not override the limits of the browser, missing fonts, device memory, browser extensions, or a compromised machine.