Why these tools never upload your files, and how to check
3 min read
Almost every free online converter makes the same promise in different words: your file is uploaded, processed and deleted. Deletion is a policy, and a policy is only as good as the company enforcing it. There is a stronger position available, and it is the one these tools take: the file is never sent anywhere in the first place.
Two architectures, one difference
A conventional converter has a server in the middle. Your browser uploads the file, the server runs a library, and the result comes back. Deleting the upload afterwards is real work, and every promise about it is a promise you cannot audit.
A local tool has no server in the middle. The page is a static file; the JavaScript that does the work is already in your browser; the file is read from disk by the same code that renders the result. There is no request to make.
The practical consequence is that the second architecture has nothing to delete, so there is nothing to get wrong.
How to verify it yourself in one minute
Check that a tool really works locally
- Open the tool pageLoad it normally, with the developer tools closed.
- Open developer toolsIn Chrome, Edge or Firefox press F12 and go to the Network tab.
- Clear the logSo only new requests show up from here on.
- Run the tool on a real fileMerge two PDFs, compress an image, hash a download.
- Look at what happenedYou will see the result being produced and nothing else. No request carries your file.
If a tool does send your file, you will see it: a POST with a multipart body, kilobytes or megabytes in size, to some endpoint. That is a one-second observation, and it is more convincing than any privacy page.
The reason the tools can be free
Processing on a server costs money per conversion, which is why services that do it either charge, limit you or advertise. When your own device does the work there is no marginal cost to pass on, so there is no reason to meter, upsell or watermark.
The one honest exception
A link-sharing tool cannot work this way. A URL has to point at something, and that something has to live somewhere other than your browser. The share tool on this site therefore does store what you paste, for a period you choose, and says so on its own page rather than hiding behind the general claim.
Open tool →Share a linkTurn a snippet or a file into a short link that expires. Stored briefly, never indexed.That is the shape of an honest privacy claim: it holds on the pages where it is true, and it names the page where it is not.
What these pages do not do
- No account, so there is nothing to link a file to.
- No third-party runtime requests on the tool pages — the OCR data and the segmentation model are served from this domain.
- No claim about your file being deleted, because it was never received.
- No fabricated numbers: there are no user counts, ratings or success rates on any page, because none are measured.
A local tool is not a security audit. It means your file is not transmitted; it does not mean the code is free of bugs. For a document you would not open at all, use a device you control and accept the same risks you would with any software.
Tools used in this guide
Questions about this guide
- Do these tools work without internet?
- The PDF, image and text tools do, once the page has loaded. The two on-device AI tools download a model on first use, so they need a connection once.
- How can this be free?
- There is no server doing per-file work, so there is no per-file cost. Sites that charge are paying for compute you are providing yourself.
- Is anything at all collected?
- The pages are static and the tools run locally. The share tool stores only what you deliberately paste, for the expiry you choose.
- What about the AI tools — do they call an API?
- No. The recognition engine and the segmentation model are served as files from this domain and executed by your browser on WebAssembly.
All guides
- How to merge PDF files without uploading themCombine several PDFs into one document, in the order you choose, entirely in your browser. No upload, no account, no page limit.
- How to split a PDF: extract a page range or one file per pagePull out the pages you need from a PDF, or turn a document into one file per page — locally, without uploading it.
Written and maintained by the FreeOnlineBox project. Every tool named in this guide runs on the reader’s own device; no file described here is uploaded to check it.