How FileSwiftly works (and why your files stay private)
Most online PDF tools upload your document to a server, process it there and send it back. FileSwiftly does the processing inside your browser instead. Here is what that means in practice.
The traditional way: upload, wait, download
With a server-based tool, your file travels over the internet to a data center, is stored there while it is processed, and the result is stored again until you download it. Reputable services delete files after an hour or so, but you have to take that on trust — and the document has still existed on someone else’s computer.
The FileSwiftly way: the browser does the work
When you open a FileSwiftly tool, your browser downloads the tool’s program code — the same way it downloads any web page. When you pick a file, the browser reads it from your disk into memory. The program code then works on the file right there: copying pages, re-encoding images, encrypting. The finished file is created in memory and offered to you as a download.
At no point is your document, its name or any password you type sent to our server. There is no upload endpoint to send it to.
The engines under the hood
| Component | Used for | License |
|---|---|---|
| PDF.js (Mozilla) | Rendering page thumbnails and previews, PDF to JPG, PDF to Text | Apache 2.0 |
| pdf-lib | Merging, splitting, rotating, page numbers, watermarks, editing and signing | MIT |
| QPDF compiled to WebAssembly | AES-256 encryption, decryption, repair and lossless compression | Apache 2.0 |
| fflate | Creating ZIP downloads and decoding compressed images | MIT |
The heavy engines are only downloaded when you actually use a tool, which is why tool pages open instantly.
Verify it yourself
- Open any tool, for example Merge PDF.
- Open developer tools (F12, or Cmd+Option+I on a Mac) and select the Network tab.
- Add your files and run the tool. You will see JavaScript and WebAssembly files being fetched, but no request that sends your PDF.
- For extra certainty, add one file, then disconnect from the internet and run the tool again — it keeps working.
Limits of in-browser processing
Your device does the work, so a phone takes longer than a desktop on very large files, and extremely large documents (many hundreds of megabytes) can exceed the browser’s memory. Tasks that need large server-side engines, such as faithful Word conversion and OCR, are not offered yet for the same reason.
Questions
Can FileSwiftly see my files?
No. Files are read and processed by code running in your browser. No request containing your file is ever sent to our server.
How can I check that nothing is uploaded?
Open your browser’s developer tools, choose the Network tab and run any tool. You will see the page and library files being downloaded, but no upload of your document.
Does it work offline?
Yes. Open a tool and add a file (this loads the processing engine), then disconnect from the internet: the tool keeps working, because it never needs our server to process anything.