Which PDF tools work without uploading your file, and which ones need the server?

"Online PDF tool" usually means "upload your file to someone's server". For a lot of jobs that is not necessary any more: a modern browser can open a PDF, move its pages around, lock it with a password or pull the text out of it on its own, without the file leaving the computer. Some of the tools here work that way. Others cannot yet, because the work needs software a browser does not have.

This page says which is which, in one place. The same information is on every tool page, in the marks under the heading and in the question "What happens to my file?", but it is easier to compare when it is a list.

How to tell on any tool page

Under the heading of each tool there are three short marks. One of them answers this question:

• Stays on your device means the whole job runs in your browser. Nothing is uploaded. You can watch the network tab of your browser while it works and see no file go out.
• Deleted after processing means the file is sent to our server over an encrypted connection, the result is made there, and the working copy is deleted in the same request, as soon as the result is built.
• Secure & private is used on the signing and redaction tools, which also work on the server and also delete the copy, and where the thing people worry about is the certificate or the removed text rather than the file itself. Their own "What happens to my file?" answer gives the detail.

In both server cases we keep a record that the tool was used, and nothing else: not the file, not its name, not what was in it. The Security page describes the handling in full.

Tools that never upload the file

These do all their work inside the browser.

Two details worth knowing:

• Image to Text and PDF to Text recognise scanned pages in the browser as well. Only if your browser cannot run the reader are the scanned pages sent to the server as images, read there and deleted once they have been read. The tool tells you when that happens.
• JPG, PNG and WebP to PDF are made in the browser, with one exception: a set that includes an iPhone HEIC photo is sent to the server, because most browsers cannot open HEIC. The HEIC to PDF page says so, and so does the JPG page.

Tools that use the server, and delete the copy when the result is built

Why these need a server: converting a Word file faithfully means laying it out with real fonts and the rules of a word processor; recognising a scanned page well, in dozens of languages, takes a model far bigger than a web page can carry; compressing pictures inside a PDF without wrecking them is slow work that would stall a phone. Each of these tools says on its own page what it does with the file. Request Signatures is the one tool where the document is kept, for 30 days, because the people you sent it to need to open it; its page explains that.

What this means in practice

• A contract you would rather not send anywhere can still be merged with its appendix, have its pages put in order, be locked with a password and have its text copied out, all without leaving your computer.
• If the job is on the server list, the file travels over an encrypted connection and the copy is gone once the result exists. That is the same whether you are signed in or not.
• A tool's own page is the place to check, because the list above changes as more work moves into the browser. The marks under the heading are read from the same source as this post, so the two cannot disagree for long.
• If you are choosing between services rather than between tools, free online PDF tools compared puts the free limits, file sizes and signature checking of five services in one table.