Browser 106

max 1GB

Inspector media/bpm-detector

BPM Detector

Overview

Drop a track and this tool finds its tempo the way a beat tracker does: it builds an onset envelope from the audio, autocorrelates it to find the period, then refines the answer by scoring a click train against the real transients. You get a BPM to one decimal place and — more usefully — the beat grid drawn straight onto the waveform, so you can see whether the lines sit on the drums instead of taking a number on trust. Where two metrical levels fit equally well, as with drum'n'bass at 174 and its half-time feel at 87, both are offered rather than one being picked for you. The same decode also gives you the key, the loudness and the peak, because they cost nothing extra once the file is open.

Beat-match a setGet exact tempi for a crate of tracks so you know what mixes with what before you open the deck.
Set a project tempoFind the BPM of a reference track and start your session at the same tempo.
Check a tagged BPMLibrary tags are often wrong or rounded. This measures the file itself.

Set

Media Tools 16

Neighbours

01 Audio Converter 02 Compress Video 03 Extract Audio from Video 04 Audio HLS Stream Generator 05 HLS Stream Generator 06 Key & Camelot Finder

Specification

Command: media.bpm_detector
Set: Media
Input: MIXED
Output: —
Max file: 1GB
Batch: single file

MPEG WAV FLAC MP4 OGG OPUS AAC WEBM

Runtime

Engine: ffmpeg-wasm 0.12
Threads: — workers
Isolated: —
WebGPU: —
Memory: —

Transport 0 B

The file is opened, worked on and written back inside this tab. No upload step exists in this tool — there is nowhere for the bytes to go.

Keys

Search: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/

How it works

Drop a track

Any audio file, or a video with an audio track. It is decoded on your device — nothing is sent anywhere.

Read the tempo

The BPM appears first, with the beat grid drawn over the waveform beneath it.

Check the grid

Press play and watch the playhead cross the lines. If they land on the drums, the tempo is right.

Frequently asked

How accurate is the BPM?

On material with a clear pulse the period is accurate to a few thousandths of a beat, and the grid stays aligned across a whole track. The harder question is which metrical level you meant — 87 or 174 — and where two fit equally well the tool shows both and lets you choose rather than guessing.

Why does it sometimes show half or double the tempo I expected?

Because both are correct descriptions of the same recording. Autocorrelation finds a pulse; nothing in the audio says whether a listener would tap it once or twice a bar. When the two readings score closely the confidence drops and the alternate is offered next to the main figure.

Is my music uploaded?

No. The file is decoded and analysed entirely inside your browser using Web Audio and a WebAssembly-free DSP pipeline that runs in a worker. Nothing leaves your device.

What formats can I use?

Anything your browser can decode — MP3, WAV, FLAC, M4A/AAC, OGG and Opus, plus the audio track of most video files.

Keys

Search: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/

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