ManyDJ
Two decks, automatic BPM and key detection, sync, effects, sampler and mix recording — all running on your own machine.
This is the whole rig. Have a look around — jog wheels, pads, loops, effects, the mixer and the recorder are all here. When you want to hear it work, drop a track on a deck or press Demo track. Every song you add is kept in Your tracks, under the decks, one press from either deck.
Master, headphones & recording
Headphone cue needs a second output device (USB audio interface, split cable or a Bluetooth headset). Pick it above, press CUE on a channel, and blend between the cue bus and the master with the CUE/MASTER knob.
Sampler
Tap a pad to fire it. Drop your own audio onto a pad to replace the sound, Shift-click to loop it, right-click to reset it. Shift + 1–8 fires the pads from the keyboard.
Track library
Drop a folder here to load a whole crate. Each track is analysed on your device for tempo and key, then drag it onto a deck — or use the A / B buttons. The same tracks sit in the Your tracks bar under the decks, so you rarely need to open this panel. Tracks stay for this visit; they are never uploaded.
MIDI controller
Plug your controller into USB, press Connect a MIDI controller and allow MIDI when the browser asks. Move anything on it and Last signal shows what arrived. Then press Learn mode, click a control on screen — a knob, fader, button, pad or jog wheel — and move the one on your controller that should drive it. Mappings are kept in this browser, and the controller is picked up again on your next visit. Use ENC on a row if that knob is an endless encoder.
Web MIDI works in Chrome, Edge, Opera and Firefox on a computer, and in Chrome on Android. Safari has none, so it cannot work on an iPhone or iPad.
Settings
Auto gain sets each channel's trim from the analysed loudness so both tracks sit at a similar level. Auto analyse runs tempo and key detection on every track added to the library. Settings, MIDI mappings and mixer preferences are stored in this browser only.
Free online DJ software — mix, sync, scratch and record two tracks
ManyHand DJ is a two-deck DJ workstation that runs entirely in your browser. Load a track onto each deck and it is analysed on the spot: the tempo is measured, a beat grid is laid over the waveform, and the musical key is named and given a Camelot code so you know what will mix with what. From there you have the tools of a club setup — beat sync with phase lock, key lock so a track can be sped up without turning into a chipmunk, eight hot cues, beat loops and rolls, a slicer, ten beat-synced effects, a sampler, a full mixer with per-channel filters and headphone cue, MIDI controller support and one-button recording of the mix.
Nothing is uploaded. Every file you load is decoded, analysed and mixed on your own machine with the Web Audio API — the analysis runs in a background worker and the playback engine runs on the audio thread, which is what keeps scratching and looping tight.
What is in the box
How to mix two tracks
- Drop two tracks onto the decks and wait a moment for the BPM and key to appear. No music to hand? Press Demo track on each deck — the page builds one, and they are four BPM and a Camelot step apart on purpose.
- Start deck A, then press SYNC on deck B — its tempo and beat phase snap to deck A's.
- Press CUE on channel B and find the point you want to bring it in from, using your headphones.
- Play deck B on a phrase boundary and ride the crossfader across while pulling the bass out of the outgoing track with the LOW knob.
- Use the key badges to line up harmonically: the same Camelot number, one step up or down, or the same number in the other letter, all tend to work.
Can I try it without any music files?
Yes. Press Demo track on a deck and the page synthesises one for you — a full arrangement, not a loop — then analyses it like any other track. Load one on each deck and the two are four BPM and one Camelot step apart, so sync and harmonic mixing both have something to do.
Are my songs uploaded to a server?
No. Tracks are decoded, analysed and mixed entirely in your browser. The audio never leaves your device.
How does the BPM and key detection work?
A background worker builds a spectral-flux onset envelope from the track, fits candidate tempos against it to find the BPM and the first beat, and matches a chroma profile against the 24 major and minor keys. The result is the beat grid you see on the waveform and the Camelot code on the deck.
What if the detected BPM or beat grid is wrong?
Click the BPM badge on the deck. You can type an exact tempo, tap it in, halve or double it when the detector picks the wrong metre, nudge the grid in 5 ms steps, mark the downbeat under the playhead, or re-run the analysis.
Can I use my own DJ controller?
Yes, in browsers with Web MIDI support (Chrome, Edge, Opera and Firefox on a computer, and Chrome on Android; not Safari). Open the MIDI controller panel, press Connect a MIDI controller, turn on Learn mode, click a control on screen — a knob, fader, button, pad or jog wheel — and move the matching one on your controller. Mappings are saved in your browser and the controller is picked up again on your next visit.
Can I hear the next track in my headphones first?
Yes, if you have a second output device. Pick it in the Master panel, press CUE on a channel, and use the CUE/MASTER knob to blend what you hear.
Can I record my mix?
Yes — press REC in the Master panel. Stopping produces a WAV file you can play back and download from the same panel.
Can I play only the vocals of a song, or take them out?
Yes. Each deck has a VOCALS ONLY and a NO VOCALS button (keys A and I). When a track loads, the page separates out whatever sits in the centre of the stereo image — in most songs, the lead vocal — and a thin bar under the buttons shows how far it has got. Press the lit button again to bring the whole song back. This is centre-channel extraction, not an AI model: some centred drums or instruments can come through with the voice, and a mono recording cannot be split at all.
Where do the songs I add go?
Into the Your tracks bar under the decks. Every song you add, or drop on a deck, stays there for the visit with its tempo and key, and its A and B buttons load it straight onto that deck. Nothing is uploaded, and the list is cleared when you close the page.
What audio files can I use?
Anything your browser can decode: MP3, WAV, M4A/AAC, OGG, Opus and, in most modern browsers, FLAC.
More free music tools: Song Remixer · Online Piano · Drum Machine · Metronome
Only mix audio you own or have the rights to use.