Free converter · Extract audio
Convert WebM to M4A
Short answer
Drop your WebM file into the converter below and download the M4A file. It runs in your browser with FFmpeg, for files up to 100 MB; nothing is uploaded. Only the sound is kept: the video track is dropped and the audio is saved as AAC audio in M4A, audio only.
Maximum file size: 100 MB. The first conversion loads a ~30 MB converter engine, once per visit. Nothing is uploaded - conversion runs on your device.
Extract audio from WEBM into M4A. · Extract audio · Browser-side via FFmpeg WASM - nothing uploaded.
Key takeaways
- The 2.11 MB WebM file became a 163 KB M4A file (-92.3%), about 130 kbps for the 10 second clip.
- The result holds: Audio: aac 48000 Hz 2 ch.
- In your browser the same conversion of a 3 second clip took 0.26 seconds on the single-thread engine; natively, the 10 second clip took 0.31 seconds.
- Next to it: WebM to AAC (-92.2%), WebM to AVI (+25.1%), WebM to FLAC (-24.0%).
Measured: WebM to M4A
The converter's own ffmpeg arguments, run on a 10 second 1920 × 1080 excerpt of Big Buck Bunny (an animated film, not camera footage) saved in WebM. The browser column is the same arguments on the single-thread WebAssembly core with a 3 second excerpt, in a headless run; your device will differ. Results describe this clip and these encoders.
| Check | Result |
|---|---|
| Mode | Audio re-encoded |
| Input | WebM, 2.11 MB |
| Output | M4A, 163 KB (-92.3%) |
| Output streams | Audio: aac 48000 Hz 2 ch |
| Time, native, 10 s clip | 0.31 s |
| Time, browser engine, 3 s clip | 0.26 s |
A re-encode decodes and encodes every frame or sample, so the time grows with the length of the file.
WebM vs M4A
| WebM | M4A | |
|---|---|---|
| Full name | WebM (open web format) | MPEG-4 audio |
| What is inside | VP8, VP9 or AV1 video with Vorbis or Opus audio | AAC (or Apple Lossless) audio in an MP4 container |
| Compression | Lossy | Lossy or lossless |
| Best for | Video on web pages; YouTube accepts it, most short-form apps do not | Apple devices and voice memos |
What you get
AAC audio in M4A, audio only. Extract audio from WEBM into M4A.
Planning a bigger file
These are estimates scaled up from the 10 second clip. Real files differ with content, resolution and bitrate, so treat them as an order of magnitude, not a promise.
| Length of the video or recording | Input size (like ours) | M4A size | Time in your browser |
|---|---|---|---|
| 1 minute | 12.62 MB | 976 KB | 5 seconds |
| 10 minutes | 126.24 MB | 9.76 MB | 52 seconds |
| 1 hour | 757.44 MB | 58.56 MB | 5.2 minutes |
A WebM file of this kind reaches the 100 MB limit of the converter after about 8.3 minutes; converting it would take roughly 43 seconds on the single-thread engine, and the M4A would be about 8.11 MB.
WebM and M4A next to their neighbors
The same clip through other conversions with the same source or the same target.
| Conversion | How | Size change | Time (native) |
|---|---|---|---|
| WebM to M4A | Re-encode | -92.3% | 0.31 s |
| WebM to AAC | Re-encode | -92.2% | 0.32 s |
| WebM to AVI | Re-encode | +25.1% | 1.5 s |
| WebM to FLAC | Re-encode | -24.0% | 0.13 s |
| WebM to MKV | Re-encode | +51.6% | 5.0 s |
| WebM to MOV | Re-encode | +51.9% | 5.1 s |
| WebM to MP3 | Re-encode | -92.4% | 0.25 s |
Choosing M4A
M4A: MPEG-4 audio. Apple devices and voice memos. WebM: WebM (open web format). Video on web pages; YouTube accepts it, most short-form apps do not.
- Keep your original: a re-encode is a copy of a copy.
- If the destination states the format it accepts, use that and nothing else.
Questions people ask
Is this WebM to M4A converter free and private?
Yes. It is free, needs no account and runs entirely in your browser, so the file never leaves your device.
Will converting WebM to M4A reduce quality?
The audio is re-encoded to M4A.
Is there a file size limit?
Files up to 100 MB. The first conversion downloads a converter engine of about 30 MB once per visit; larger files are better handled by a desktop app such as HandBrake or FFmpeg.
How do I convert WebM to M4A?
Choose the file in the converter above and download the M4A. It runs in your browser with no upload.
Will converting WebM to M4A reduce quality?
M4A adds no loss of its own. Keep the original file.
Why did the file size change by -92.3%?
The target codec and settings decide the size. This 10 second clip came out at 163 KB, about 130 kbps.
How long does it take?
A 3 second clip took 0.26 seconds in the browser engine in our test; time grows with the length of the file.
How long will a WebM file of 100 MB take?
At the speed we measured in the browser engine, about 43 seconds for a file like our clip. Your device and the content will change it.
Is my file uploaded?
No. The conversion runs in your browser.
Is there a size limit?
Files up to 100 MB. The first conversion downloads a converter engine of about 30 MB once per visit.
More converters
Sources and how we checked
- MDN: Media container formats
- MDN: Web audio codec guide
- MDN: Image file type and format guide
- FFmpeg documentation: stream copy
- FFmpeg Documentation: ffmpeg (stream selection, -map, -c copy) (read 2026-10-09)
- MDN: Web audio codec guide (read 2026-10-09)
- Blender Foundation: Big Buck Bunny (CC BY 3.0), the clip used for the measurements (read 2026-10-09)
Reviewed October 8, 2026. What the converter writes was measured with ffprobe on the same FFmpeg build your browser downloads; format descriptions follow MDN's media guides.