How free browser BPM detection works
Beats per minute (BPM) is how many pulses fit into one minute of music. Automatic detectors look for repeating energy — usually kick drums or strong transients — and estimate how often those events occur. On a clear electronic beat the result is often stable. On ambient music, spoken word, or swing-heavy performances, the detector may lock to a half-time or double-time feel.
Browser tools can decode audio with the Web Audio API and run detection locally. Unreleased demos do not need to be uploaded to a stranger’s server for a basic tempo check. Use half/double buttons, tap tempo, and your ears before you commit a project tempo.
- Open the free tool at /app.html.
- Drop a 20–40 second section with drums when possible.
- Read BPM and confidence.
- Try half or double if the groove feels wrong.
- Confirm with tap tempo for eight bars.