BPM Detector

What it does

Tempo is one of the first things DJs, producers, and curious listeners want to know. BPM Detector estimates beats per minute from an audio file using onset strength and autocorrelation — classic signal-processing ideas that run entirely in JavaScript. Results are estimates, not studio-grade grid analysis. Clear drum patterns and steady grooves produce the most stable readings; rubato performances, ambient textures, or heavily swung material can be less certain. Because the analysis is local, you can check tempo for private recordings without uploading them to a cloud service.

What BPM detection can—and cannot—tell you

BPM means beats per minute, a common way to describe musical tempo. DJs use tempo estimates when preparing transitions; musicians use them to set a metronome, compare grooves, or plan practice. This detector analyzes changes in short-window audio energy and looks for repeating rhythmic patterns.

The result is an estimate rather than a guaranteed beat grid. Half-time and double-time interpretations are common, and syncopated, rubato, ambient, or percussion-light music can be difficult to measure. Try a section with a steady beat and compare the displayed value with what you hear.

What makes a tempo estimate more reliable?

A steady rhythmic passage usually gives the detector more useful information than an intro, breakdown, or ambient section. Kick drums, snares, hi-hats, and repeated accents can all contribute to the pulse, but syncopation and sparse percussion may confuse the estimate. If the result feels twice or half as fast as the music, consider the common double-time or half-time interpretation.

BPM is a practical reference for DJ preparation, practice, arranging, and comparing musical sections. The displayed value is an estimate from the selected audio, not a manually verified beat grid, so use it as a starting point and confirm it by listening or tapping along.

For tonal information, try the Key Detector. To prepare a shorter rhythm-focused section, use Audio Trimmer.

How to use it

Tip: Try a section with a clear, consistent beat. If the estimate seems off by a factor of two, check whether a half-time or double-time reading better matches the groove.