You get an MP4 with H.264 video and AAC audio, a file that QuickTime, phones, browsers and editing apps open without a plugin.
To convert WMV to MP4, add the WMV file, keep MP4 as the output format and download the result. WMV cannot be copied into an MP4 container, so the video is re-encoded to H.264. That makes the file playable almost everywhere. In our test a 2.18 MB WMV became a 1.17 MB MP4, though other files will differ, and a DRM-protected WMV cannot be converted at all.
Transfers use HTTPS, and files converted on the free tier are deleted after 24 hours, so the result is not a long-term archive. Quality depends on the source file, so open the MP4 file once before you share it.
WMV (Windows Media Video)
A Microsoft video format built on the ASF (Advanced Systems Format) container. Files usually carry Windows Media Video codecs such as WMV3 (also called VC-1) with Windows Media Audio, and Windows Movie Maker in Windows XP offered it as an output. Some players, especially on Apple devices, need a converter to open it.
MP4 (MPEG-4 Part 14)
The container behind most phone, camera and web video today. It is built around H.264 video and AAC audio, which Macs, iPhones, Android phones, browsers, smart TVs and editing apps all play without extra software.
A 640 × 360 WMV test clip (WMV 8, 10 s) made by us, converted on indox.org
Renaming movie.wmv to movie.mp4 does not work, because the video inside is still a Windows Media stream. The converter decodes it and writes H.264 video with AAC audio, so the new file is an MP4 inside as well as by name.
H.264 players and editors expect an even width and height. When the converter has to re-encode, it rounds an odd frame size down to the next even number, which changes the picture by at most one pixel.
The MP4 is written with its index at the front of the file. That lets a browser or phone begin playback straight away without waiting for the whole clip to arrive.
In our test the converter wrote H.264 High video at about 803 kb/s (CRF 23) and AAC-LC stereo audio at about 117 kb/s, from a 640×360 WMV that carried Windows Media audio.
Drop the WMV file on the box or choose it from your device. Keep the original; it is the only copy that has not been compressed twice.
Check that MP4 is the output format, then start the conversion and wait for it to finish. In our test a 10-second clip took 6.9 seconds from the click to Completed.
Save the MP4 and watch it from start to end on the device you care about. Check that the sound stays in step with the picture, especially in a long clip.
You hand over a WMV file and take away an MP4 with H.264 video and AAC audio, ready for a Mac, an iPhone, an editor or a web page. Nothing is installed on your computer. The page says up front that the video is re-encoded and that DRM-protected files cannot be converted.
The upload box shows the live size limit before you add a file. Signing in raises it; a paid plan does not change it.
WMV in, MP4 out. Pick another output on the converter if you need a different format.
Files are encrypted in transit over HTTPS and processed on indox infrastructure.
Free-tier files are kept for 24 hours after the job finishes, then deleted automatically.
| What you see | Why | What to do |
|---|---|---|
| The conversion fails | The WMV may be protected with DRM, or the file is damaged | Check that the WMV plays in the software that holds its licence, or try another copy of the file |
| The sound drifts from the picture | Old WMV clips can have uneven timing, more so in long videos | Try a constant frame rate in ffmpeg or VLC, or cut the clip into shorter parts before converting |
| The MP4 looks softer than the WMV | The picture was compressed a second time | Keep the WMV as your master and use the MP4 only for sharing |
| You need the sound only | The MP4 still holds the picture | Use MP4 to MP3 on the result |
Older video files at a smaller size
iPhone and Mac video that plays anywhere
Video for phones, TVs and editors
Browser recordings you can share
| Compared on | WMV | MP4 |
|---|---|---|
| Container | ASF, a Microsoft wrapper | ISO base media file format, derived from QuickTime |
| Typical codecs | WMV3 (VC-1) video with Windows Media Audio | H.264 video with AAC audio |
| Where it plays | Windows; many Mac, phone and web players need extra software | Macs, iPhones, Android phones, browsers, TVs and editors |
| Standard | Developed by Microsoft; Windows Movie Maker in XP could save it | ISO/IEC 14496-14, published in 2003 |
| Converting between them | Cannot be copied into MP4 | Needs a re-encode from WMV |
Facts checked on November 4, 2026
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Add the WMV file to the converter in your browser, keep MP4 as the output and download the result. Nothing is installed on the Mac. The MP4 opens in QuickTime, which cannot play the WMV.
Add the file to the converter in your browser and download the MP4. You do not need to install a codec pack or an extra program. Windows already plays WMV, so the usual reason to convert is to use the clip on another device or in an editor.
Yes, because the conversion runs on indox infrastructure and the phone does none of that work. Open the converter in the phone's browser, choose the WMV file and download the MP4 when it is ready. A very large video is easier to handle on a computer.
No. The name is only a label. Inside, the file is still a Windows Media stream, and most players will refuse it or show a blank picture. The video has to be decoded and re-encoded as H.264 to become an MP4.
A little, yes. WMV and MP4 are both lossy, so the picture is decompressed and compressed again. In our test the result scored PSNR 42.8 dB and SSIM 0.9916 against the source, which is very close, and it never makes the video sharper than the original. Keep the WMV as your master copy.
It depends on the file. Our 2.18 MB sample WMV came out as a 1.17 MB MP4, 46.6% smaller, because the old WMV 8 codec is less efficient than H.264. A WMV that was already compressed hard can come out larger.
Yes. In our test the index sat at the front of the MP4, so a browser or phone can begin playback straight away.
MP4 cannot store the codecs that WMV usually uses, which are WMV3 (VC-1) for video and Windows Media Audio for sound. Both have to be converted, to H.264 and AAC. Some formats can be moved into a new container untouched, but this pair cannot.
No. A WMV locked with DRM cannot be read by the converter, so the conversion fails. If you own the content, play it with the software that holds its licence. Do not expect a blank or blocky MP4 to be a workable copy.
Old WMV clips, especially long ones, can have uneven frame timing, and the audio can drift against the picture after conversion. As general advice, a tool such as ffmpeg or VLC can force a constant frame rate, or you can cut the clip into shorter parts before converting. Our test clip stayed in step, but it was only 10 seconds long.
Both can do it on your own computer if you are comfortable installing and configuring them. The result is the same kind of re-encode to H.264 and AAC. This page is the shorter route when you only have a file or two and do not want to set up software.