What happens when you upload a PDF

Most online PDF sites work the same way: your file is uploaded to their servers, processed there, and sent back for you to download. Reputable sites encrypt the transfer and delete files after a set time, often an hour or a few hours. But while it's there, your document is on someone else's computer, under their security, their staff and their country's laws, and you have to take their word for when it's deleted.

For a takeaway menu that doesn't matter. For a passport scan, a payslip, a medical report or a client's contract, it might, and many employers' data-protection rules forbid uploading personal or confidential data to services they haven't approved.

The alternative: tools that run in your browser

Modern browsers are powerful enough to process PDFs themselves. A browser-based ("client-side") tool sends the program to your device, instead of sending your file to a server. The file is read, changed and saved by your own browser, and never travels over the internet.

Every tool on Timesnap PDF works this way: merging, splitting, compressing, editing, signing, locking and unlocking, and converting photos and spreadsheets. There are no accounts and no file history on our side, because we never receive the files.

How to tell if a tool uploads your file

  • Read how it says it works. Tools that run on your device usually say so plainly. If the privacy policy talks about deleting files from its servers after a while, your files are uploaded.
  • Watch what happens. An "Uploading…" bar, or a long wait on a slow connection before anything happens, usually means your file is going to a server.
  • If you're technically minded: open the browser's developer tools (F12), go to the Network tab, and watch for a large request when you add a file.

Merge PDFs privately in four steps

  1. Open Merge PDF.
  2. Drop two or more PDFs. They open in your browser; nothing is sent.
  3. Drag the page thumbnails into order, mixing pages from different files if you like.
  4. Press Merge PDF and download your combined file.

Open Merge PDF

Other good habits with private PDFs

  • Lock sensitive PDFs with a password (AES-256) before emailing them, and send the password another way, such as by text message.
  • Remove hidden details, such as the author's name, before sharing a document outside your organisation.
  • Covering text with a white box doesn't delete it: the words can still be copied out. To truly remove text, use a proper redaction tool, or turn the pages into pictures.