Split a song into stems
Takes the first half-minute of an audio or video file and separates it into four tracks you can play and download. The model is downloaded to your device and runs there — the file never leaves this tab.
Drop an audio or video file here
MP4 · MOV · M4A · WAV · MP3 — the first 30 seconds are used
Pressing the button downloads about 295 MB of runtime and model. It is fetched once and kept by your browser — the next file starts straight away.
Separation runs on the processor: about 1 min for 30 seconds of audio. That is why this is a preview.
Where does my audio go?
Nowhere. It is opened inside this browser tab and never uploaded. That matters here: an unreleased mix is exactly the kind of file you should not be handing to a stranger's server.
Why only 30 seconds?
Because separation is slow on a processor. We measured it: 7.8 seconds of audio takes about 15 seconds to separate, so 30 seconds takes roughly a minute and a full three-minute song would take six. This tool is a preview — enough to hear how clean the split is before you commit to a desktop tool for the whole track.
How good is the separation?
This is Demucs v4, the same model most desktop stem tools use, at full precision. We checked it with numbers rather than by ear: we mixed a speech recording, a 60 Hz sine and a click track together, then measured how closely each output stem matched each ingredient. Vocals matched the speech at 0.999, bass matched the sine at 1.000, drums matched the clicks at 0.985, and every stem was near zero against the others.
Which files can I use?
MP4, MOV, M4A, WAV and MP3. Those are the ones your browser can open on its own, so we never ship another decoder. MP3 took longest to add — not because it is heavy, but because it has no container: it is a bare stream of frames, and something has to find the frame boundaries before the browser's decoder will take it. We wrote that part; nothing extra is downloaded.
Why is the download so large?
The model is about 300 MB and it is the whole tool. There is no smaller build of Demucs v4 that we could verify, and shipping a quantised one that quietly degrades would be worse than being honest about the size. It is fetched once and your browser keeps it.
Why does it not use my graphics card?
Because we only measured and verified the processor path. Other tools here try the graphics card first, but an unverified fast path that produces subtly wrong audio would be harder to notice than a slow one. If we measure a graphics-card path that gives the same numbers, we will switch.
Other tools
- Compress videoShrink an MP4 in your browser. No 30MB toolchain to download — your device does the work.
- Audio extractorPull the sound out of a video. Nothing is re-encoded, so nothing is lost.
- Video to GIFTurn a clip into a looping GIF. Your device does the work — nothing is uploaded.
- Video trimmerCut a clip out of a video without re-encoding it. Nothing is lost, and it takes seconds.