The Hidden Privacy Risk of Online File Converters — WebConverter

Need to convert a JPEG to PNG? You search the web, pick the first result, and upload your file. The converted image downloads within seconds. Simple — but what actually happened to your file in those few seconds?

Your Files Go to a Server You Don't Control

The vast majority of online image converters work by uploading your file to a remote server. The server runs the conversion, stores the result, and sends it back. The problem is what happens between those steps — and after.

When you upload a file, you are trusting that the service:

• Does not store a copy of your image beyond the conversion
• Does not analyse, index, or train AI models on your data
• Does not share your file with third parties
• Actually deletes the file when it claims to

Some services state in their privacy policy that uploaded files are deleted after a set period — 30 minutes, 24 hours, or "after processing." But there is no way for you to verify this. The file left your device the moment you clicked "Upload."

What Could Go Wrong

Personal Photos

Photos contain EXIF metadata: GPS coordinates, camera model, timestamps, and sometimes even the software used to edit them. Uploading a batch of holiday photos to a converter shares this metadata with the server operator — even if all you wanted was a format change.

Business Documents

Screenshots of internal dashboards, scans of contracts, medical images — all of these are routinely converted online. If the server is breached, misconfigured, or simply logging more than it should, sensitive data is exposed.

Malware Injection

In early 2025, the FBI issued a public warning about malicious file converter websites that inject malware into the files they return. The converted image looks normal, but the downloaded file contains hidden payloads designed to compromise your system.

The Alternative: Convert Locally

WebConverter.app takes a fundamentally different approach. Your files never leave your device. The conversion runs entirely inside your browser using WebAssembly — compiled C++ code executing on your own CPU.

Here is what that means in practice:

• No upload — your file is read from disk into browser memory. It is never sent over the network.
• No server processing — there is no back end. The conversion logic runs client-side.
• No storage — there is nothing to delete because nothing was ever stored remotely.
• No third-party access — your data stays in the browser tab until you close it.

You can verify this yourself: open your browser's developer tools, go to the Network tab, and watch while you convert a file. You will see zero outbound requests carrying your image data.

How to Protect Yourself

If you cannot use a fully client-side tool, here are some precautions:

1. Strip metadata first — remove EXIF data before uploading. Many operating systems let you do this in the file properties dialog.
2. Read the privacy policy — look for explicit statements about file retention and third-party sharing.
3. Avoid unknown sites — stick to tools with a known track record and open-source code you can inspect.
4. Prefer client-side tools — if the conversion can run in the browser, there is no reason to upload your files.

Try a Converter That Respects Your Privacy

WebConverter.app supports PNG, JPEG, BMP, TGA, HDR, EXR, and KTX2 — all running locally, with zero data transfer. It is free, open source, and you can install it as an offline app.