Is it safe to use online file converters?

What happens to your file

Most online converters work like a post office. You upload your file, their server converts it, and you download the result. For a short time, and sometimes much longer, a copy of your file sits on a computer owned by someone else.

Many services say they delete files after an hour or a day. Some do exactly that. But you usually cannot check it, and you cannot know who else can access their servers in the meantime.

The real risks

For a photo of a sunset, the risk is small. For other files, it is worth thinking twice:

• Private documents. Contracts, payslips, bank statements, medical letters and ID scans contain exactly the kind of information that is valuable to criminals.
• Data breaches. Any company that stores files can be hacked. A file that was never uploaded cannot leak from someone else's server.
• Unclear policies. Some free services are paid for by advertising and tracking, and their privacy policies can allow more than you expect.
• Work rules. Many employers do not allow staff to upload company documents to outside services. Using one can break your contract or data protection law.

The hidden data in your files

Files often carry more than you can see. Photos from phones can contain the exact GPS location where they were taken, the date and time, and the phone model. PDFs and office documents can contain the author's name, earlier versions of text, and comments.

When you upload a file, all of this goes with it. When you share a converted file, it may still be inside. Good tools let you remove location data from photos before you share them.

Tools that run in your browser

There is another way. Modern browsers are powerful enough to convert many files on your own computer or phone. With this kind of tool, the website loads once, and then the work happens on your device. Your file is never sent anywhere.

That is how OnDevice Tools works. Because there is no upload, there is nothing to store, nothing to delete and nothing to leak.

How to check any tool in one minute

You can see for yourself whether a tool uploads your file. On a computer:

1. Open the tool in Chrome, Edge or Firefox.
2. Press F12 to open the developer tools and click the Network tab.
3. Add a file and start the conversion.
4. Watch the list. An upload shows up as a request whose size is about as big as your file, often of the type "POST" or "fetch". A tool that works on your device shows no such request.

A quick safety checklist

• Prefer tools that process files on your device for anything private.
• Read the privacy policy: does it say clearly what happens to your file?
• Avoid tools that ask you to create an account just to convert one file.
• Remove location data from photos before you share them.
• Keep your original file until you have checked the result.