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Free · In-browser · No upload

BPM Detector, Checker & Analyzer.

Check a track's BPM, compare half-time and double-time interpretations, inspect tempo changes, and export the evidence — locally in your browser.

Before-and-after illustration of BPM Detector: Unknown music track becomes BPM and Camelot result through Estimate beat and key.
Before → process → afterSee the signal story, then hear it in the workspace.

MEASUREMENT MAP

Tempo Pulse Evidence

Turn a signal into evidence you can inspect. A useful analyzer connects the raw trace, the measurement window and a clearly labeled result without pretending that one number explains the whole recording.

Before-and-after illustration of BPM Detector: Unknown music track becomes BPM and Camelot result through Estimate beat and key.
Unknown music trackEstimate beat and keyBPM and Camelot result
An analysis path: a bounded signal window produces comparable metrics and a visual trace while preserving the context needed to interpret them.
Open the full signal breakdownBest source, processing logic, limits and three-pass listening check
  1. Unknown music track

    Start with the right material

    DJ library triage, choosing the right metrical count, spotting broad tempo changes and documenting an unknown track before editing.

  2. Estimate beat and key

    Understand the transformation

    Up to 16 bounded segments use onset energy, stable adjacent-onset intervals and normalized autocorrelation fallback; chroma matching supplies a separate key and Camelot estimate.

  3. BPM and Camelot result

    Verify the usable result

    A chosen BPM interpretation, evidence label, tempo segment map, key/Camelot suggestion, source facts and versioned JSON/CSV analysis.

Beat confidence

Where this workflow stops

Evidence labels summarize repetition and usable coverage, not accuracy. The map is not a beat grid; swing, sparse onsets, polyrhythms, rubato and harmonic ambiguity can still mislead either estimate.

THREE-PASS CHECK

Make the final decision by ear

  • Use the same window and settings when comparing two files.
  • Treat estimates as evidence, not as a substitute for listening.
  • Export or note the measurement context alongside the result.

How to check BPM, tempo changes and key

  1. Drop a track into the BPM analyzer — MP3, WAV, FLAC and other browser-decodable formats work.
  2. Wait while a serialized header/metadata preflight estimates memory before PCM decode, followed by bounded onset and segment analysis. No selected audio is sent to AudioWrench.
  3. Compare the explicit half-time, original and double-time values, then choose Use this BPM for the count that matches the groove.
  4. Inspect the evidence label, source facts and segment tempo map before exporting a matching JSON or CSV analysis receipt.
  5. No file handy? Tap the tempo pad in time with the music to calculate BPM from your recent taps.

This free online BPM detector, BPM checker and tempo analyzer measures repeating onset spacing, then keeps the common metrical ambiguity visible instead of hiding it behind one number. The selected BPM can help with DJ library prep, sample matching and project-tempo triage. The musical key and Camelot code are separate tonal estimates. All results are evidence-led suggestions, not guaranteed ground truth.

BPM Detector: quick answer and technical limits

Quick answer: A bounded tempo and key analyzer with selectable half/original/double BPM, segment-level stability evidence and portable JSON/CSV receipts.

Best for
DJ library triage, choosing the right metrical count, spotting broad tempo changes and documenting an unknown track before editing.
How it works
Up to 16 bounded segments use onset energy, stable adjacent-onset intervals and normalized autocorrelation fallback; chroma matching supplies a separate key and Camelot estimate.
What you get
A chosen BPM interpretation, evidence label, tempo segment map, key/Camelot suggestion, source facts and versioned JSON/CSV analysis.

Know before you use it: Evidence labels summarize repetition and usable coverage, not accuracy. The map is not a beat grid; swing, sparse onsets, polyrhythms, rubato and harmonic ambiguity can still mislead either estimate.

Public browser workflow evidence

Question: Can the real UI recover controlled 80, 100, 128 and 160 BPM pulse trains and disclose its intentional half/double-time folding at 60 and 200 BPM?

Observed result: All 6 cases passed. Exact grid: 80→80 BPM, 100→100 BPM, 128→127.7 BPM, 160→160 BPM. Declared half/double-time interpretations: 60→120 BPM, 200→100 BPM.

Evidence boundary: These fixtures are steady synthetic click grids. Swing, syncopation, rubato, changing tempo and mastered music remain outside this wave.

Network observation: No audio-payload or cross-origin requests were observed during this published workflow.

Open the public benchmark, method and fixture →

Privacy: Selected audio is processed in this browser and is not uploaded to AudioWrench. Normal page assets can still be requested as described in the privacy notice. Privacy details →

FAQ

How do I find the BPM of a song?
Drop the song into the BPM analyzer. It measures changes in short-window energy, compares repeating onset spacing, and returns a tempo estimate. You can also tap the pad if the beat is only in your head.
Why can a BPM detector return half-time or double-time?
The same pulse pattern can be counted at different metrical levels. A 70 BPM half-time groove can share onset spacing with a 140 BPM count, so the tool shows half, original and double variants and lets you choose the interpretation that matches the music.
Can this BPM checker detect tempo changes?
It creates a bounded segment tempo map across the decoded track. The map flags broad metrical or tempo variation, but onset evidence alone cannot prove whether a 90 versus 180 BPM difference is a real tempo change or half/double-time counting. It is not a beat-by-beat tempo grid.
Is the evidence label an accuracy score?
No. Strong, moderate or limited evidence describes onset repetition, usable segment coverage and agreement between segments in this file. It does not measure correctness against a human-labelled ground truth, so confirm important tempo and key decisions by ear.
Is my music uploaded to a server for BPM analysis?
No selected audio is uploaded to AudioWrench. Decoding, onset analysis, tempo mapping and key estimation run in this browser. Normal page assets can still be requested as described in the privacy notice.