How to verify that a PDF tool processes files locally

A “private” label is not enough to prove where document processing happens. You can test useful parts of the claim with a synthetic PDF, browser developer tools and an offline run. These steps mirror the evidence SnackPDF uses for its browser-local implementation.

1. Use a safe test document

Create a PDF containing a unique phrase and a harmless filename, or use the SnackPDF sample PDF. Never begin an investigation with a confidential document.

2. Watch network requests

1. Open the browser's Network panel and clear existing entries.
2. Choose the test PDF and complete an operation such as compressing the sample locally.
3. Inspect request URLs, methods and payloads. The file name, unique phrase and PDF bytes should not leave the page for processing.

Ordinary requests for the application, its WebAssembly engine and managed hosting can still occur while online. The meaningful question is whether document data is transmitted.

3. Inspect browser storage

Check localStorage, IndexedDB and Cache Storage. An offline-first tool may cache its application files, but it should not persist your selected PDF or finished result unless it clearly says so. SnackPDF caches routes, scripts, styles and its local engine; selected and generated documents stay out of persistent application storage.

4. Repeat the complete task offline

After the tool says it is ready, disconnect from the network, reopen a cached page and finish the same operation. Successful offline processing is strong evidence that the document transformation does not depend on a processing server, though it cannot audit browser extensions, the operating system or hosting infrastructure.

5. Look for reproducible evidence

Prefer a precise processing boundary, source and licence information, named limitations and tests that use unique markers. SnackPDF publishes its network, storage, determinism, fidelity and offline checks, its source and licences, and its privacy explanation.