WMV → MP3
WMV to MP3 converter
The Windows Media Audio (WMA) track in the WMV is decoded and re-encoded to MP3, and the video is ignored. WMA is lossy, so the MP3 is a second lossy generation.
…or drag files and folders here. Add as many as you like — everything is processed on this device.
.asf .avi .f4v .flv .m4v .mk3d .mka .mkv .mov .mp4 .qt .wmv
In one paragraph
WMV was Windows’ own video format for a decade: Windows Movie Maker exports, old webinar and training recordings, and countless clips saved from the early web. Its audio is almost always Windows Media Audio, a codec that Macs, iPhones, Android phones and every web browser lack. Converting to MP3 is the simplest way to make that audio playable anywhere.
Sonic Batch reads the ASF container and decodes WMA version 1, 2 or Pro with a WebAssembly build of FFmpeg running in your tab, so it works on a Mac, a Chromebook or a phone without installing Windows codecs. The video stream is never decoded, which keeps the job quick even for long recordings.
Does this change the audio quality?
WMA and MP3 are both lossy, so this conversion costs one generation. WMV files typically carry WMA at 64–192 kbps; an MP3 at the same bitrate or one step higher keeps the extra loss very small.
- DRM-protected WMV files (from old online stores and rental services) cannot be decoded.
- WMA Voice and lossless variants are rare in video; the common WMA v2 and Pro decode normally.
- Only the first audio track is extracted.
A worked example
Converting an archive of old training videos for a podcast feed
- Drop the folder of WMV files into the queue.
- Choose the Podcast/voice preset for spoken content.
- Check the first finished MP3 to confirm the level and quality.
- Convert the rest and download the ZIP.
Match the WMA bitrate the file shows
Once the engine reads the file, its row shows the source bitrate. Pick the same MP3 bitrate or one step higher. Old WMV webinar and screen recordings are often 32 to 64 kbps mono speech, where a 64 kbps mono MP3 sounds identical and stays small.
Supported formats, limits and browser notes
Sonic Batch decodes with the browser when it can (faster, no engine download) and falls back to the self-hosted WebAssembly engine when it cannot. Every combination below works in every listed browser; the column only tells you which decoder does the work.
| Input | What it is | Chrome | Firefox | Safari | iOS |
|---|---|---|---|---|---|
| WMV | Windows Media video in an ASF container. Audio is almost always WMA (Windows Media Audio). | Engine | Engine | Engine | Engine |
| AVI | Legacy Windows video container from camcorders, older cameras and DivX/Xvid files. Audio is usually MP3, PCM or AC-3. | Engine | Engine | Engine | Engine |
| MP4 | The standard video container. Its audio track is almost always AAC. | Native | Partial | Native | Native |
| MOV | QuickTime video from iPhone and DSLR cameras. Audio is normally AAC or PCM. | Partial | Engine | Native | Native |
| MKV | Open video container used for films, TV recordings and OBS captures. Audio is often AAC, AC-3, DTS, Opus or FLAC. | Partial | Partial | Engine | Engine |
| FLV | Flash-era web video, still produced by some stream recorders. Audio is AAC or MP3. | Engine | Engine | Engine | Engine |
| Output | Encoder | Bitrates / depth | Sample rates | Tags |
|---|---|---|---|---|
| MP3 | libmp3lame | 32–320 kbps | 8–48 kHz | Yes + artwork |
- Max per file
- 400.0 MB
- Max per queue
- 4.00 GB
- Max duration
- 4:00:00
- Max archive
- 1.50 GB
These are enforced ceilings, checked before any decoding starts, not measured maximums — a file over the limit is rejected rather than allowed to exhaust the tab’s memory. Real-world capacity is lower on older phones, which is why the scheduler runs one file at a time on iOS and Safari.
Where your audio goes
Nowhere. Your file is read from disk into this browser tab with the File API, decoded and encoded by code running in that same tab, and handed back to you as a download. It is never transmitted.
That is a structural property of the application, not a policy promise: there are no API routes, no server actions and no third-party processing services in this project, so there is nothing capable of receiving a file. The page’s Content-Security-Policy also restricts connections to this origin, and the automated test suite includes a browser test that fails if any network request during import, preview, conversion or download carries media bytes.
The trade-off, stated plainly: results live in your tab’s memory until you download them. Closing or reloading the page discards them. There is nothing on a server to recover, because nothing was ever put there.
Troubleshooting
It says the file is protected or unsupported.
WMV files sold or rented through old Windows Media stores carry DRM. They cannot be decoded outside the licensed player.
The duration only appears after a while.
Browsers cannot read WMV at all, so the queue waits for the engine to open the file before it can show the length.
Can I convert WMA audio files here?
This page is about WMV video. WMA audio files decode with the same engine through the batch converter.
Frequently asked questions
How do I convert WMV to MP3 on a Mac?
Open this page in Safari or Chrome, add the WMV files, and press Convert all. Nothing needs installing; the decoder runs in the browser.
Does WMV to MP3 lose quality?
Slightly. WMA is already lossy, and encoding to MP3 is a second lossy step. At a matching bitrate the difference is hard to hear.
Are files uploaded?
No. The conversion happens on your device and the page cannot transmit files.
Does it also accept ASF files?
Yes. ASF is the container WMV uses, and .asf files are read the same way.