Hola PDF
How it works
Most online PDF tools upload your file, work on it on their servers, and promise to delete it. Hola PDF brings the tools to your file instead.
The engines run in your browser
When you open Hola PDF, your browser downloads the app and two PDF engines, compiled to WebAssembly so they run at close to native speed:
| Engine | What it does here |
|---|---|
| PDFium, the PDF engine inside Google Chrome | Opens documents, draws pages, reads their text, turns images into pages. |
| qpdf | Assembles the PDFs you download, keeping form fields, bookmarks and links. |
Your file is read from your disk into the page, the engines work on it there, and the result goes back to your Downloads folder. No step involves a server.
Why it can't upload
Every page of holapdf.app is served with a Content Security Policy that only allows connections to holapdf.app itself (connect-src 'self'), and holapdf.app has nothing that accepts a document. The one script loaded from elsewhere is Cloudflare's visit counter (Cloudflare Web Analytics), and it too can only report to holapdf.app. (The one page that loads someone else's code, Paddle's checkout for buying Pro, lives on its own address, buy.holapdf.app, where it can't reach these pages.) If a mistake in the app's code tried to send your file to a server, the browser would block the connection.
Check it yourself
- Turn off your Wi-Fi. Once Hola PDF has loaded, it keeps working: open a PDF, rearrange it, download it.
- Watch the network. Open your browser's developer tools, choose the Network tab, then open and export a document. You'll see the app's own files and Cloudflare's analytics script load once, and one small report to holapdf.app/cdn-cgi/rum for each page you visit, which counts the visit. Nothing leaves when you work.
What that means for you
Contracts, medical records, statements, IDs: you can work on documents you shouldn't upload. It is also fast, since nothing waits for an upload, and it works on a plane.
The trade-off is that the work uses your device. Very large files need memory, and on phones the iPhone and iPad apps (Hola PDF for iPhone, iPad and Mac) are the better tool.