WMV to MP4 Converter
FileFlip converts WMV to MP4 entirely inside your browser, using WebCodecs and FFmpeg compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert a WMV file to MP4?#
- Drop your WMV file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to MP4 and the conversion starts on its own. FileFlip usually downloads nothing, falling back to 30.8 MB of WebAssembly if your browser cannot encode these codecs itself, then runs WebCodecs and FFmpeg on your own machine.
- Save the MP4 file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting WMV to MP4 lose quality?#
Sometimes. When the codecs inside the WMV file are ones the MP4 container can hold, the streams are copied straight across and nothing at all is lost. When they are not, the file has to be decoded and encoded again, and that step does cost a little quality.
Is it safe to convert WMV files online?#
Yes, because nothing is uploaded. FileFlip converts WMV files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What WMV to MP4 actually does to the file#
Converting WMV to MP4 runs on WebCodecs and FFmpeg, usually downloads nothing, falling back to 30.8 MB of WebAssembly if your browser cannot encode these codecs itself, copies the streams through when the codecs fit and re-encodes when they do not.
| Engine | WebCodecs and FFmpeg |
|---|---|
| Conversion path | One step: WMV → MP4 |
| Downloaded to your browser | Nothing in most browsers, or 30.8 MB if yours cannot encode these codecs itself |
| Quality | Lossless when the codecs fit, lossy when they do not |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Encoded streams | Sometimes | Survives for some files and not others. |
Worth knowing before you start:
- the FFmpeg fallback is an LGPL build, so a re-encode produces MPEG-4 Part 2, VP8, VP9, or Theora rather than H.264 or H.265
- whether the browser can do this without FFmpeg depends on the codecs it exposes through WebCodecs
- the encoded streams are copied when the file's codecs fit the target container, and re-encoded when they do not
What is a WMV file?#
A WMV file holds video encoded with one of Microsoft's Windows Media Video codecs inside an ASF container, usually alongside a Windows Media Audio track, and often with Microsoft's DRM applied.
Keep a file as WMV when it is staying on Windows and feeding software that expects it, which is where the format has always worked best.
Convert WMV to MP4 to get the video off Windows, since Macs, phones, browsers and TVs will not play it as it stands.
What is an MP4 file?#
An MP4 file holds video, audio, subtitle and chapter tracks together in the MPEG-4 Part 14 container, the structure ISO standardised from Apple's QuickTime format and the way most video is stored and shared today.
Choose MP4 when the file has to play somewhere you do not control, which covers anything uploaded, emailed or handed to another person.
Convert an MP4 to something else when the destination is not a player: pulling out the audio, making a GIF, or moving into Matroska to keep several subtitle and audio tracks in one file.
WMV to MP4 questions people ask#
Why won't my WMV file play on a Mac or iPhone?
WMV was never made to run outside Windows. Apple has no decoder for it, QuickTime has never opened it, and Flip4Mac, the plugin that used to bridge the gap, stopped being maintained around 2015. VLC plays WMV on macOS today because it carries its own decoders. Converting to MP4 is the fix if the file needs to work in Photos, iMovie or on an iPhone.
Is WMV a codec or a file format?
WMV is really a family of codecs, and a .wmv file is an ASF container holding one of them. The version matters: WMV 7, 8 and 9 are all different, and VC-1 Advanced Profile is not backward compatible with WMV 9. That is why a very old WMV can fail in modern software that dropped the earlier decoders while a newer one plays without trouble.
What is the difference between WMV and WMA?
WMV is Microsoft's video codec and WMA is its audio counterpart, and they usually travel together, since the audio track inside a WMV file is normally WMA. Both sit in the same ASF container underneath. A .wma file holds audio on its own, which is why it plays in music apps while a .wmv needs a video player.
Why can't I play a WMV video I bought years ago?
A purchased WMV that suddenly refuses to play is almost certainly protected by Windows Media DRM, which checks a licence with a server before letting the video open. Microsoft has moved on to PlayReady and many of the stores that sold WMV content are gone, taking their licence servers with them. Files in that state cannot be converted, because the video inside is encrypted rather than merely wrapped.