mp3tomidiAudio Tools
Free Online Tool

BPM & Key Detection Online Free

Detect the tempo and musical key of any audio file instantly in your browser.

Drop your audio file here

or click to browse

Supports MP3, WAV, OGG, FLAC · Max 50MB

How It Works

Step 1

Upload Your Audio

Drag and drop or browse for any MP3, WAV, OGG, FLAC, M4A, AAC, or WebM file up to 50 MB.

Step 2

Automatic Analysis

Our WebAudio-based algorithms decode the audio and detect tempo and musical key entirely in your browser.

Step 3

View Results

See the detected BPM, musical key, mode, and confidence scores displayed instantly.

Example Output

128Beats Per Minute
A MinorMusical Key
Confidence94%

Detected from a 45-second electronic dance track

Features

Everything you need for fast, accurate audio analysis.

100% Private

All analysis runs locally in your browser. Your audio files are never uploaded to any server.

Instant Detection

Get BPM and key results in seconds thanks to optimised WebAudio and FFT-based algorithms.

Multiple Formats

Supports MP3, WAV, OGG, FLAC, M4A, AAC, and WebM — virtually any audio file you have.

Confidence Scores

Each result comes with a confidence percentage so you know how reliable the detection is.

Works Everywhere

Use it on any modern browser — Chrome, Firefox, Safari, Edge — on desktop or mobile.

Waveform Visualisation

See a real-time interactive waveform of your audio with playback controls.

Trusted by DJs and Producers

I use this before every gig. Faster than any desktop tool.

Sarah M.

DJ & Producer, Berlin

Accurate BPM detection even on tracks with tempo variations. Impressive for a free tool.

Alex K.

Remixer, Tokyo

My students love seeing the key detection results in real time during class.

Carlos R.

Music Teacher, Barcelona

Why Detect BPM & Key?

Knowing the tempo (BPM) and musical key of a track is fundamental for anyone working with audio. DJs rely on BPM to create seamless beat-matched transitions between songs, while music producers need key information to layer melodies, harmonies, and bass lines that sit perfectly together. Even casual musicians benefit — if you want to jam along with a recording, knowing its key saves you the guesswork.

Traditionally, detecting BPM and key required expensive desktop software or a trained ear. Our free online tool removes those barriers entirely. Upload any audio file — whether it is an MP3 from your music library, a WAV export from your DAW, or a voice memo you want to pitch-shift — and get accurate results in seconds. Because the analysis runs entirely in your browser using the Web Audio API and fast Fourier transform (FFT) algorithms, your files never leave your device, keeping your music completely private.

The tool analyses onset density to determine beats per minute and uses chromagram-based pitch-class profiling to identify the musical key and whether the track is in a major or minor mode. Confidence scores accompany every result, giving you a clear indication of how certain the algorithm is. This is especially useful for tracks with complex arrangements, tempo changes, or ambiguous tonal centres.

Whether you are a DJ building a set list, a producer arranging a remix, a music teacher preparing materials, or a content creator matching background music to a video, accurate BPM and key data lets you work faster and make better creative decisions. Best of all, there is nothing to install and no account required — just drop your file above and start analysing.

Our BPM finder uses advanced onset-density analysis and autocorrelation to deliver accurate tempo detection results. Whether you call it a BPM detector, tempo finder, or beat counter, the underlying algorithm is the same — optimized for real-world music with varying dynamics. BPM detection is essential for DJs beat-matching tracks, producers setting project tempo, and music students analyzing song structure.

Frequently Asked Questions

What audio formats are supported?
We support MP3, WAV, OGG, FLAC, M4A, AAC, and WebM files up to 50 MB in size. If your file is in a different format, you can convert it using a free tool like FFmpeg before uploading.
How accurate is the BPM detection?
Our BPM detection uses onset-density analysis and autocorrelation techniques that typically achieve accuracy within 1-2 BPM for steady-tempo tracks. Every result includes a confidence percentage so you can gauge reliability. Tracks with tempo changes or complex rhythms may produce lower confidence scores.
How does key detection work?
The algorithm computes a chromagram — a time-frequency representation mapped to the 12 pitch classes — and compares it against major and minor key profiles. The best-matching profile determines the detected key and mode (major or minor).
Is my audio file uploaded to a server?
No. All processing happens locally in your browser using the Web Audio API. Your file is never transmitted over the internet, ensuring complete privacy.
Can I detect the BPM and key of a YouTube video?
You need to have the audio file locally first. Download the audio from the video (where legally permitted), then upload the file to our tool for analysis.
What is the minimum and maximum audio length?
The audio must be at least 1 second and no longer than 10 minutes. For best key-detection accuracy, we recommend at least 15-30 seconds of representative audio.
What BPM is typical for hip hop, EDM, and pop music?
Hip hop: 80-100 BPM, EDM: 120-150 BPM, pop: 100-130 BPM, jazz: 120-180 BPM. These are general ranges — many subgenres and modern tracks break these conventions.
Can the tool detect tempo changes within a song?
Our algorithm detects the dominant tempo. For tracks with significant tempo changes (rubato, accelerando), the confidence score will be lower. For best results, analyze sections with consistent tempo.
Is this a BPM finder or tempo detector?
Both. Our tool serves as a BPM finder and tempo detector in one. It analyzes audio onset density to determine beats per minute, functioning as an accurate BPM detector for any genre — from hip hop to classical.

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BPM & Key Detection Online Free | mp3tomidi