How BPM detection works
The tool decodes your audio to raw samples, measures the energy in short 20 ms windows, and finds the peaks — the loud moments that usually correspond to kick drums and snares. It then histograms the time between those peaks and converts the most common interval into beats per minute.
When it works well — and when it doesn't
Detection is reliable (±2 BPM) for music with a clear, steady beat: electronic, pop, rock, hip-hop, dance. Genres without prominent percussion — ambient, classical, free jazz, spoken word — may not produce a clean BPM, because there genuinely isn't a single tempo to find. If a track you know is 128 BPM reads as 64 or 256, the engine locked onto a half- or double-tempo harmonic.