Convert WMV to MP4, privately in your browser

WMV: the Windows video format that nothing else plays

WMV (Windows Media Video) was Microsoft’s video format in the Windows XP, Vista and Windows 7 years. Windows Movie Maker saved its projects as WMV, many screen recorders and webcam apps produced WMV files, and a lot of corporate training videos and old website clips still exist only in this format. WMV files usually carry WMA (Windows Media Audio) sound, and some use the related .asf extension.

Outside of older Windows software, support is poor. Web browsers cannot play WMV, Macs and iPhones do not open it, Android support is patchy, and most social networks and messaging apps refuse it. Converting to MP4 with H.264 video and AAC audio is the simplest way to make these videos watchable and shareable again.

What happens when you drop a WMV file

Since browsers cannot decode WMV or WMA, Vidmini converts the file on your device first, using its built-in fallback converter: FFmpeg compiled to WebAssembly. During this step the page shows "Preparing this format for your browser…" and a percentage. When it finishes, a notice tells you that the file was converted on your device first, and Vidmini produces the final MP4.

On first use, your browser downloads the 32 MB converter from vidmini.com. It is only program code; the WMV itself never leaves your computer or phone. Nothing is uploaded, at any point.

Honest expectations: re-encoding, speed and the 1 GB limit

WMV to MP4 is never a simple container swap: the Windows Media video is re-encoded to H.264 and the WMA sound to AAC. Vidmini uses high-quality settings, so the MP4 looks and sounds as close to the original as possible, but it is a re-encode, not a lossless copy. Many WMV files were exported at low resolutions for small file sizes; the MP4 will keep that resolution, it cannot add detail that was never there.

The fallback converter is single-threaded WebAssembly, so WMV conversions are noticeably slower than MP4 or MOV conversions, which use your browser’s native decoders. A Movie Maker slideshow of a few minutes usually converts quickly; an hour-long recording takes patience.

Files up to 1 GB are accepted. Larger WMV files will not work with this tool. Videos protected by DRM, such as some purchased or rented WMV files, cannot be converted either.

Private by design

Your WMV is read and converted inside the browser. There is no account, no watermark and no tracking cookies, and the Content Security Policy only lets the page talk to vidmini.com for its own code. That matters for family videos and work recordings alike.

When the MP4 is ready, "Continue with this file" lets you compress it, trim it or extract its audio without selecting the file again.