Are Free Online Tools Safe? What Happens to Your Files

Search for any file conversion and you get dozens of free tools. Almost all of them work the same way: you upload your file, their server processes it, and you download the result. For a holiday photo that is fine. For a signed contract, a payslip or a scan of your ID, it deserves a second thought.

What happens when you upload a file

Your document is copied to a machine you do not control, in a country you may not know, where it is stored for some period you cannot verify. Reputable services delete files after an hour or a day and say so plainly. Others say nothing. A few reserve broad rights over uploaded content in terms nobody reads.

Even with good intentions, an uploaded file is exposed to whatever happens to that company: a misconfigured storage bucket, a breach, an acquisition, a change of policy. The safest file is the one that was never sent anywhere.

Why it does not need to be uploaded at all

Browsers have become genuinely capable. JavaScript running in your tab can read a file from disk, decode a PDF, resize an image with hardware acceleration, hash text with the same cryptographic primitives your operating system uses, and write a new file back to your downloads folder. None of that requires a server.

That is how every tool on this site works. There is no upload endpoint, because there is nothing to upload to.

How to check for yourself

You do not have to take anyone's word for it, including ours. Three ways to verify:

1. The aeroplane test. Load the page, turn off wi-fi and mobile data, then use the tool. If it still works, nothing is being sent.
2. The network tab. Press F12, open Network, and use the tool. Watch for a large outgoing request when you select your file. Local processing produces none.
3. Read the wording. Sites that upload usually say so somewhere — "files are deleted after 2 hours" is a promise about files they have. A tool that processes locally has no such promise to make.

The honest trade-offs

Local processing is not always better, and pretending otherwise would be dishonest.

• Very large files are limited by your device's memory. A server with 64 GB of RAM will handle a 2 GB PDF that a phone cannot.
• Some tasks genuinely need a server: OCR on scanned documents, converting to Word with layout preserved, anything using a large model.
• Old devices are slow. Compressing thirty photos happens in seconds on a modern laptop and takes a while on a five-year-old phone.
• Nothing syncs. A note saved in your browser is on that device only. That is the privacy feature and the limitation at the same time.

Simple rules worth following

• Never upload identity documents, bank statements or medical records to a free converter. Use a local tool, or your own computer's built-in features.
• Assume anything you upload could persist indefinitely. Decide with that assumption, not with the retention policy.
• Strip metadata before publishing photos. Camera files often carry GPS coordinates.
• Keep the original of anything you compress or convert — the process is one-way.
• For truly sensitive work, prefer offline desktop software you have installed, over any website at all.

The general point is not that servers are bad. It is that a task which can be done on your own device should be, because the safest copy of your document is the one that only ever existed on your machine.

Frequently asked questions