About FileXvert

Why this service exists

Most online converters require you to upload the file: it is copied to a server, converted, kept for a while, then sent back. For a holiday photo, the stakes are low. For an identity document, a payslip, a contract or an unreleased work video, every remote copy is one more exposure the user has no control over.

FileXvert starts from the opposite principle: send the tool rather than the file. Current browsers run compiled code almost as fast as installed software, so it becomes possible to convert a video or edit a PDF without the content leaving the device. It is a verifiable guarantee, not a promise: once the engine has loaded, these conversions work even offline. The only exceptions are a few office conversions, flagged before upload.

How it works

FFmpeg, the reference library for audio and video processing, is compiled to WebAssembly and run by your browser. Your file is read from disk, transformed in memory, then saved back to your machine. PDF editing follows the same principle with pdf-lib and pdf.js.

That choice has a direct consequence: speed depends on your machine, not on our servers. A recent computer will convert faster than a phone, and a very large file can hit the tab's memory limit.

Under the hood

• Video, audio and images: FFmpeg, the reference encoder used by most editing software, compiled to WebAssembly and run in a worker, apart from the page.
• Multi-core when possible: conversion pages enable cross-origin isolation (COOP and COEP headers), which lets FFmpeg use several processor cores. Without it, a slower single-core build takes over.
• Documents: pdf.js, Firefox's PDF engine, to read and extract text; pdf-lib to produce, merge and edit PDFs; zip.js to read Word (DOCX) files.
• Lossless remuxing: an H.264 MOV is copied as is into an MP4 container, without re-encoding, whenever you ask for neither reduction nor a resolution change.
• Office conversions on the server: Word, PowerPoint, ODT, RTF and HTML to PDF, Word to ODT, RTF, EPUB, HTML and PDF/A with LibreOffice and Chromium, PDF to Word, Excel and PDF/A with pdfplumber and Ghostscript. The service is isolated, has no Internet access, and erases each file as soon as the result is returned.

What the service can do, and what it does not

FileXvert converts between the main video formats (MP4, MOV, MKV, AVI, GIF, and WebM as input), audio (MP3, WAV, FLAC, AAC, OGG, M4A), images (JPG, PNG, WebP, and AVIF or SVG as input) and documents (PDF, PDF/A, Word, Excel, PowerPoint, ODT, RTF, CSV, HTML, EPUB, TXT, Markdown), with bridges between categories: a video becomes an audio file, an image becomes a PDF, a PDF becomes images or a PowerPoint presentation. The free plan handles files up to 100 MB, Premium up to 2 GB; in both cases, your device's memory sets the real limit.

A few office conversions cannot be done faithfully in a browser: Word, PowerPoint, OpenDocument, RTF or HTML documents converted to PDF or between each other, PDF to Word, Excel or PDF/A. They go through our server (LibreOffice, Chromium, Ghostscript), in an isolated service with no Internet access, after a notice shown before upload. Other conversions are deliberately not offered, because they would fail: producing AVIF or WebM, producing SVG, or recognising the text of a scanned document (OCR).

What we record

• No file kept. Most conversions never reach us. The office conversions done on the server are erased as soon as the result is returned.
• Conversion metadata for signed-in accounts: input and output formats, size, duration, success or failure. Enough to show a history, not enough to rebuild a file.
• Cookie-free audience measurement. A visitor is represented by a digest renewed every day; no IP address is kept, and two visits a day apart cannot be linked together.

How we check what we claim

Every FFmpeg command the site builds, every compression level and every format pair offered is covered by automated tests, run before each release. A conversion only appears in the list if it has actually been verified.

The figures published in our practical guides (resulting sizes, fidelity measured with the SSIM index) come from real conversions, made with exactly the site's settings, on files described in each article. When a measurement reveals a flaw, we fix the tool: that is how the default quality of JPG and WebP images was raised in October 2026.

How the service is funded

Through Premium subscriptions and ads shown to free accounts. Conversion pages may show a sponsored link while processing, without loading third-party ad scripts. Ads cannot access your files or their contents, and Premium subscribers never see them. The plans are detailed on the Pricing page.

Who publishes the site

The publisher, the host and the data controller are identified in the legal notice. Data processing is detailed in the privacy policy.

Contact us

A question, a missing format, a bug: contact@filexvert.fr — or through the contact form. The FAQ already covers the essentials.