Tap or click the left panel in time with the track on your left deck, and the right panel for the track on your right deck.
The big number is the tempo in BPM, averaged over your recent taps — it settles after four or five taps and keeps refining as you go.
The smaller number is the beat count, with the bar and the beat within the bar underneath (four beats to the bar).
If you tap on the half-beat, use the ×2 / ÷2 line to read the tempo you meant.
On a keyboard: A or ← for the left deck, L or → for the right.
Pause for a few seconds and the deck goes idle; your next tap starts a fresh count.
Reset left / Reset right clear one deck, Reset all clears both.
Listening through an input
Listen on either deck reads the tempo from an audio input instead of your taps. Your browser will ask for permission the first time; nothing is recorded and no audio leaves your device.
A reading takes a few seconds to settle, and the percentage next to “Listening” is how sure it is. The bar under the deck name is the input level — if it is not moving, the app is not hearing anything.
One microphone hears the room, not one deck: during a mix it picks up both tracks at once, so both decks will show the same number.
For a genuinely separate reading per deck, feed a stereo line output from your mixer into the device and set the left deck to the left channel and the right deck to the right channel.
If you have already tapped a deck, the app uses that to settle whether it is hearing the tempo or half/double of it.