Privacy
Converting a file without uploading it: how it works, and how to check
Most online converters work the same way: you upload the file, a server converts it, then you download the result. FileXvert does the opposite: the server sends you the tool, and your file never leaves your device. This article explains what that means in practice, how to check it in two minutes without taking our word for it, and what this architecture cannot do.
The classic model: your file travels
With a traditional online converter, the file goes through three stages. It is first uploaded to the service's servers, often hosted in another country. It is then stored for the duration of the conversion, sometimes queued behind other users' files. Finally, the result is kept for a few hours or days so that you can download it.
None of this is dishonest in itself, but each stage raises a question you cannot answer yourself: who has access to the server, how long is the copy really kept, what happens to backups, has the service ever been breached? For a holiday photo, the stakes are low. For a payslip, an identity document, a contract or an unreleased work video, they are much higher.
The FileXvert model: the tool travels, not the file
When you open a conversion page, your browser downloads a program: FFmpeg, the audio and video encoder used by most editing software, compiled to WebAssembly. WebAssembly is a code format that every recent browser can run at a speed close to that of installed software.
When you pick a file, the browser reads it from your disk and hands it to that program, which runs in a worker, an execution thread isolated from the page. The result is built in memory, then offered for download. Documents follow the same principle with other libraries: pdf.js to read the text of a PDF, pdf-lib to produce one.
At no point is the content of the file, or even its name, sent to our servers. They only serve the site's pages and the program files, which are the same for everyone.
Check it yourself in two minutes
A privacy promise is only worth something if it can be verified. Here are two tests anyone can run, without any particular skill.
- The offline test: pick a file and an output format, then click the preparation button, which downloads the conversion engine. Now turn off your Wi-Fi or switch to airplane mode, and start the conversion: it runs to the end. A service that needed to send your file would fail immediately.
- The network test: on a computer, open the browser's developer tools (F12 key), Network tab. Start a conversion and watch the requests: you may see the conversion program being loaded, but no request whose size matches your file.
- The file name test: convert a file with a unique name, for example test-privacy-7f3a.mov. That name does not appear in any outgoing request.
These tests are worth more than any reassuring wording, ours included.
What the site still loads
For the sake of accuracy: FileXvert pages are not completely silent. The site measures its audience in aggregate form (page views, where visits come from), and some editorial pages, such as this guide, may display advertising after you have made your choice in the consent message.
Conversion pages, however, carry no ad network at all. They need a special isolation mode called cross-origin isolation so that FFmpeg can use several cores of your processor, and that isolation blocks third-party content. In every case, neither audience measurement nor advertising has access to the content of your files: it stays in the tab's memory.
The limits of this approach
Converting on your device has a cost: your processor does the work. On a recent computer, a video lasting a few minutes converts in somewhere between tens of seconds and a few minutes. On an entry-level phone, the same job can take noticeably longer.
Memory is the other limit. A browser tab does not get all of the machine's memory, and FFmpeg must hold both the source file and the result. That is why the free plan is limited to 100 MB per file; the Premium plan raises the ceiling to 2 GB, but your device still sets the real limit.
Finally, if your browser does not allow cross-origin isolation, for instance in some corporate setups, FileXvert falls back to a single-core build of FFmpeg. It is slower, and automatically caps video width at 1280 pixels to keep conversion times reasonable.
- Keep the tab open and in the foreground during a long conversion: some browsers slow down background tabs.
- Close memory-hungry applications if converting a large file fails for lack of memory.
- Always keep the original until you have checked the result.
When a classic online service is still the better choice
Local processing is not the best answer to everything. If you need to convert hundreds of files every day, installed software or a dedicated server-side service will be more efficient. If you work on a very old device, a server's power will make up for the machine's slowness. And some operations, such as text recognition in scanned documents (OCR), require models that FileXvert does not ship today.
For the most common use, occasionally converting a few personal or work files, in-browser processing offers a simple guarantee: a file that is never sent cannot be kept, leaked or reused by anyone.