Most free online converters work the same way: you upload a file, a server converts it, and you download the result. For a meme that is fine. For a passport scan, a bank statement or family photos, it is worth thinking about where the file goes and who can see it.
What happens when you upload a file
Once a file reaches someone else’s server, you are trusting their promises. Typically they say files are deleted after an hour or a day. They may well be. But the file has been copied, it may sit in backups or logs, it passes through their hosting and storage providers, and you cannot check any of it. A data breach, a misconfigured storage bucket or an unscrupulous operator can expose files that were meant to be temporary.
Converters also tend to collect more than files: email addresses for “premium” accounts, analytics, and advertising identifiers. That is normal on the web, but it is worth knowing what you are trading for a free conversion.
Red flags
- No privacy policy, or one that does not say how long files are kept.
- Requests to install a browser extension or desktop app for a simple conversion.
- Download buttons that lead to other software, or ads designed to look like download buttons.
- Requests for sign-up to download a file you already converted.
- Unclear ownership: no company name, no contact details.
The alternative: converters that run in your browser
Modern browsers can do much of what conversion servers do. Images can be decoded and re-encoded with the Canvas API, video can be read frame by frame, and libraries compiled to JavaScript or WebAssembly handle formats like HEIC and PDF. A converter built this way processes the file inside the page, on your device. There is nothing to delete later, because nothing was sent.
Myriadfile is built entirely this way. So are some other well-known tools, such as Google’s open-source image compressor Squoosh. The approach has limits: very large files depend on your device’s memory, and the browser must support the format. But for everyday photos, documents and subtitles it is fast, and private by design.
How to check whether a site uploads your file
You do not have to take anyone’s word for it.
- Open the converter and your browser’s developer tools (F12 on Windows and Linux, Cmd+Option+I on a Mac).
- Go to the Network tab and clear it.
- Convert a file. If you see a request whose size roughly matches your file, often a POST or PUT, the file was uploaded.
- Simpler still: load the page, turn off Wi-Fi, and try. A browser-based tool keeps working; an upload-based one fails.
Other precautions
- Keep your browser updated. In-browser tools are only as safe as the browser running them.
- Be wary of extensions. Browser extensions with permission to read all sites can see pages you use, including converters. Remove ones you do not need.
- Strip metadata before sharing. Photos can include GPS location. Converting to a new JPG in Myriadfile removes EXIF data; check other tools’ settings.
- For the most sensitive documents, prefer offline software you trust, or a browser-based tool used with the network disconnected.
The bottom line
Uploading to an online converter is not automatically unsafe, but it requires trust you cannot verify. For anything personal, choose a tool that does the work on your own device, and check it with the network tab. Read how Myriadfile works for the details of our approach.