Server vs browser vs desktop: what 'private' actually means in file converters
File converters come in three kinds: server upload, in-browser, and desktop app. Where your file goes in each, what you have to trust, and when each one makes sense.
Nitiksh Kumar3 min readKinoFlux Editor
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File converters come in three kinds. Server converters upload your file and process it on their computers. Browser converters process it inside the web page on your computer. Desktop apps process it in a real program with no web page involved. The further your file stays from someone else's server, the less there is to trust.
"Private" is used to sell all three. It does not mean the same thing in each.
The three kinds#
1. Server converters. The classic kind: Smallpdf, Adobe's online tools, CloudConvert and most big names. You upload the file, their server processes it, you download the result. Your file lives on their computer for some hours. You trust their retention policy, their security, and their business model.
2. Browser converters. The newer wave: tools that advertise "no upload." They run the conversion inside the web page using your computer's processor. Your file does not go to a server. But it still runs inside a page that loads scripts and ads from third parties, the browser caps how much memory the tool can use, large files can fail, and the tab must stay open. Private from the server, but not free of the web page.
3. Desktop apps. A real program installed on your computer, like KinoFlux Editor. No page, no scripts, no server. It works with the internet switched off, handles whole folders at once, and has no browser memory limit. There is nothing to upload because there is nowhere to upload to.
Compared side by side#
| Server converter | Browser converter | Desktop app | |
|---|---|---|---|
| Where your file goes | Their server | Stays on your computer | Stays on your computer |
| Third-party scripts running | On their server (invisible to you) | In the page, yes | None |
| Internet needed | Yes | Page must load, then no | No |
| Large files | Limited by upload and their queue | Limited by browser memory | Limited by your disk |
| Whole folders at once | Rarely | Rarely | Yes |
| What you must trust | Their policy, security, business | The page's scripts | Nothing |
When each one makes sense#
This is not a claim that servers are evil. Each kind has a place.
A server converter is fine for one quick job on a public file. Converting a meme video or a public-domain document? Upload away.
A browser converter is the better pick when you want privacy but cannot install anything, like on a borrowed computer. Run the airplane mode test first to check the "no upload" claim is real.
A desktop app is the right call for private files, big files, folders of files, or work you do every week. Passports, contracts, tax returns, family videos, work documents: if you would not email it to a stranger, do not upload it to one either. Do it on your own computer.
How to tell which kind a site is#
Open the site, turn on airplane mode, and try the tool. If it keeps working, nothing leaves your computer. If it breaks, your file was going to a server. There is a longer version of this check, with the browser's network tab, in the post linked below.
KinoFlux Editor is the third kind: a free offline toolbox for Windows and Mac with 66 tools for video, audio, images, PDFs and documents. No upload, no account, no telemetry. You can run the airplane mode test on it all day. It never needed the internet in the first place.
- privacy
- online converters
- comparison