Do I need to install anything to use PDF tools offline?

No. In PDF Case you open the site once while online; the browser saves the app’s files on your device. After that the tools open and run without a connection, in the same browser.

Is a PDF tool that works offline more private?

Yes, in one checkable way: a result produced with the network off was made on your device, so the file was not uploaded to make it. It is the simplest test of a site’s privacy claim.

Does offline mean my files are stored in the browser?

No. What is saved for offline use is the app’s own code and pages, not your documents. In PDF Case a result is kept in the browser only if you turn on “Keep results in Your files”, and it stays on your device.

Why did the page stop opening offline?

The browser’s saved copy was probably removed: by clearing browsing data, by closing a private window, or by the browser tidying up after a long time without a visit. Open the site once while online and it is saved again.

Can large PDFs be processed offline?

Yes. The limit is your device’s memory, not a file size cap set by a server. Very large files take longer and may need a computer where a phone runs out of memory.

PDF tools that work offline in your browser

A browser PDF tool works offline when its code is downloaded once and then runs on your device, so that merging, splitting or locking a file needs no server. Every tool in the PDF Case web app works this way: after the first visit, the pages open and the tools run with the network switched off.

Updated November 14, 2026

What does “works offline” mean for a web page?

A web page is usually thought of as something that lives on a server. But a page can also be a complete program: the browser downloads its code, and from then on the code runs on your computer or phone like any installed app.

Two pieces make it possible for PDF tools. WebAssembly lets a browser run the same kind of fast, compiled code that desktop PDF software is built from, so the heavy work of reading and writing PDF files can happen in the tab. A service worker, a small helper the browser keeps for a site, saves the site’s files on the device and hands them back when there is no connection, so the page itself still opens.

Why does offline matter if I am usually online?

Because of what it proves and what it saves:

Privacy: a tool that produces its result with no connection can’t have sent your file to a server to do it.
Speed: nothing is uploaded or downloaded, so a large file takes as long as your device needs, not as long as your connection allows.
Reliability: it works on a train, on a plane, behind a strict office network, or when a service is down.
No waiting in line: there are no queues, no daily limits set to save a server’s time, and no account to manage them.

How can I tell whether a PDF tool really works offline?

Test it with a file that holds nothing private:

Open the tool’s page while online and let it load fully.
Switch on airplane mode, or turn off Wi-Fi.
Choose a PDF and run the tool. A result you can open means the work was done on your device.
For the stronger test, close the tab, stay offline, and open the address again. If the page still opens, the site has saved itself on your device.

What can’t work offline?

The first visit: the code has to be downloaded once. Anything that by its nature involves another computer also needs a connection: sending a document to someone, collecting signatures from several people, keeping files in cloud storage, or features that run on a large model on a server.

The saved copy belongs to the browser. Clearing the site’s data removes it, a private window may not keep it after it is closed, and a browser can clear it for a site you haven’t visited in a long time. Then the next visit needs a connection once more.

Which PDF Case tools work offline?

All of the tools in the web app, because none of them uses a server. On the first visit the whole app is saved on your device, not just the page you opened, so a tool you have never used is there offline too. When a new version is published, it is fetched the next time you are online.

Compress PDF, Make searchable (text recognition), Scan to PDF and Office to PDF are not in the web app; they are in PDF Case for iPhone and iPad, where they also run on the device.

Pages: Merge PDFs, Split PDF, Extract pages, Organize pages, Crop pages, Page numbers.
Privacy: Redact, Remove metadata, Add password, Remove password.
Filling and marking: Sign PDF, Fill in a form, Annotate, Flatten, Watermark.
Converting: Images to PDF, Text to PDF, PDF to images, PDF to text, Extract images, Grayscale.

Tools for this

Files are processed on this device and never uploaded.

Questions

Do I need to install anything to use PDF tools offline?: No. In PDF Case you open the site once while online; the browser saves the app’s files on your device. After that the tools open and run without a connection, in the same browser.
Is a PDF tool that works offline more private?: Yes, in one checkable way: a result produced with the network off was made on your device, so the file was not uploaded to make it. It is the simplest test of a site’s privacy claim.
Does offline mean my files are stored in the browser?: No. What is saved for offline use is the app’s own code and pages, not your documents. In PDF Case a result is kept in the browser only if you turn on “Keep results in Your files”, and it stays on your device.
Why did the page stop opening offline?: The browser’s saved copy was probably removed: by clearing browsing data, by closing a private window, or by the browser tidying up after a long time without a visit. Open the site once while online and it is saved again.
Can large PDFs be processed offline?: Yes. The limit is your device’s memory, not a file size cap set by a server. Very large files take longer and may need a computer where a phone runs out of memory.