Convert a WMV file (Windows Media Video) into a genuinely playable MP4 locally - via an honest, full re-encode in your browser. No upload.
Running locally on your device ...
Running locally on your device ...
0%
Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
WMV is Microsoft's own video technology - both a codec (usually WMV3, later VC-1) and its accompanying ASF container - built for Windows Media Player through the late 1990s to 2000s, e.g. from old Windows Movie Maker exports. Unlike AVI, the video codec here is fixed: virtually every .wmv file uses WMV3 or VC-1, and unlike H.264, that codec never became a hardware or browser standard - no current phone, TV or web browser decodes it natively today, on any platform.
That is why every WMV-to-MP4 conversion with this tool is a real, full re-encode - unlike some sibling tools, there is no fast shortcut here, because the codec itself is never compatible. The tool decodes WMV3/VC-1 (and the accompanying WMA audio) using ffmpeg's own software decoder, entirely as WebAssembly in your browser, and encodes a fresh, universally playable H.264 MP4 from it.
Because this runs single-threaded (this site cannot use shared memory across threads), this re-encode is noticeably slower than a simple repackage and can take several minutes for longer clips - stated honestly rather than promising a speed this conversion cannot deliver. Everything runs locally in the browser, with your file never uploaded.
| Input formats | WMV |
|---|---|
| Output format | MP4 |
| Batch processing | No |
| Processing | Locally in your browser (WebCodecs) |
| File upload | None |
Limitations: Always a real, full re-encode - no target container losslessly holds WMV3/VC-1, there is no fast shortcut here. Runs single-threaded (no cross-origin-isolation mode on this site) and can take several minutes for longer clips. Audio is re-encoded to AAC in the process. One file per run, an honest device-dependent size/length limit applies - never a silent truncate.
No, the entire re-encode happens locally in your browser.
WMV uses the WMV3/VC-1 codec, which no browser or hardware chip can decode natively - so a real, single-threaded re-encode is always needed, not a quick repackage.
A video codec developed by Microsoft, technically related to WMV3 and used on some HD-DVD/Blu-ray titles among other places - but it never became a web or hardware decoder standard.
Not bit-identical - as with any re-encode, there is a small but visually barely perceptible quality loss at the chosen settings.
Yes, that is one of the most common origins of WMV files and works exactly like any other WMV file.
3GP to MP4 · AVI to MP4 · Analyze a media file · MTS/M2TS to MP4 · FLV to MP4