Most online PDF tools work like this: they upload your file to their servers, process it there, and hand back the result. But for documents like contracts, IDs and invoices, that means a copy of your file ends up on a server you don't control. For most structural PDF operations, that's unnecessary.
What does "on-device" mean?
On-device (client-side) processing means the whole job happens inside your browser — the file is never sent to the internet. That means three things: privacy (the file stays with you), speed (no upload/download wait, instant result) and the ability to work offline.
Tools that run in your browser
- Merge, Split, Rotate, Delete Pages, Reorder Pages — all on your device.
- Images to PDF, signing and annotating a PDF — on your device.
- Document Scanner — including the camera image, entirely on your device.
Merge On-Device — Merge your PDFs in your browser, without uploading to a server.
So does every tool run on-device?
Let's be honest: no. Heavy jobs like Word/Excel conversion, OCR and compression run on the server (they aren't practical in the browser). With AI tools, your file isn't uploaded — the text is extracted on your device and only the text is processed. So it's always clear which tool runs where.
For the most sensitive documents (IDs, contracts, health records), prefer the on-device structural tools and the document scanner; and if needed before sharing, remove sensitive data with real redaction.
Redact Sensitive Data — Permanently remove personal data before sharing.