BPM and key finder with Camelot codes
Drop an audio file and read its tempo, key and Camelot code. The song is analysed on this device.
- Nothing is uploaded
- Works offline after first visit
- Open source
- No account, no watermark
Finds the tempo (BPM) and musical key of a song from an audio file, and gives the Camelot code DJs use to match keys. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. Files longer than 15 minutes are not analysed, and after one visit and a short wait the page works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
How to read the result
- BPM is beats per minute, the steady pulse you would tap your foot to. The page folds the answer into 70 to 180, and for tempos from about 80 to 120 it also shows the half and the double, because a detector cannot always tell a slow song with busy drums from a fast one.
- Key is the home note and the scale, such as A minor. Many songs sit between a major key and its relative minor (C major and A minor use the same notes), so the page names the relative key as well.
- Camelot code is the key written as a number from 1 to 12 and a letter: A for minor, B for major. Two songs whose codes are the same, or one number apart, or the same number with the other letter, usually blend well. The Camelot wheel page lists all 24.
- Unsure means the notes in the song did not point clearly to one key. It happens with drones, drum-only tracks, heavy bass and songs that change key.
What this page does not do
- It assumes one steady tempo. A song that speeds up, slows down or is played without a click can get a tempo that matches only part of it.
- It reads a file, not a link. A streaming-service or video link cannot be analysed here, because the page never fetches anything for you; use a file you have.
- It does not find chords. It gives one key for the whole file.
- It reads up to 15 minutes. For a longer file, cut the part you want with Trim audio.
Without a file
- If you only want the tempo, the BPM finder page puts the BPM first and the key second.
- Tap along with a song you can only hear on the Tap tempo page, and check the answer against a click on the online metronome.
How it works
- Drop one or more songs, or tap to pick them. MP3, WAV, M4A, FLAC, Ogg and most other audio files work; a video’s sound works too.
- Press Find BPM and key. A three-minute song takes a few seconds.
- Read the tempo, the key and the Camelot code. Check the tempo by ear, and treat a key marked Unsure as a guess.
In your browser, not on a server
Your browser decodes the file to plain samples. music-tempo (MIT), a small JavaScript library, finds the loudness jumps (onsets) and the steady beat they line up with, and gives the tempo. The key comes from our own code: it measures how much of each of the 12 notes is in the song, using a Fourier transform, and compares that with the 24 major and minor key profiles published by Krumhansl and Kessler. All of it runs in a background worker in your tab.
Compared with upload-based tools: Some online analysers upload the song to their servers before they can answer, which matters for a demo, a stem or an unreleased track. Here the file is decoded and analysed on your device and never leaves it.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
How do I find the BPM of a song?
Drop the audio file here and press Find BPM and key. The page decodes the file in your browser, finds the beat and shows the tempo in beats per minute, with its tempo name, and the half and double readings when they are in a plausible range. If you only have the song playing and no file, use the Tap tempo page and tap along.
Why does the BPM look double or half of what I expected?
Both are the same pulse counted twice. A slow song with a busy hi-hat can be written either way, and detectors cannot always tell which one you mean. The page folds its answer into 70 to 180 BPM and, for tempos from about 80 to 120, shows the half and the double next to it. Pick the one that matches how the song feels, or that your DJ software or session expects.
How accurate is it?
It is an estimate made from the sound, not a lookup, so check it. Play the song next to a click on the online metronome, and treat a key marked Unsure as a guess to confirm by ear or on an instrument.
What is the Camelot code?
It is a way of writing the 24 major and minor keys as 1A to 12B so that keys that sound good together sit next to each other on a wheel. A is minor and B is major. A minor is 8A and its relative major, C major, is 8B. DJ software often shows it next to the BPM.
Why does it show two keys?
A major key and its relative minor use exactly the same notes, so from the notes alone it is often a close call which one the song treats as home. The page shows its best answer and names the relative key, because that is the most common near miss. Listen for which note feels like the place the music comes to rest.
Can I paste a YouTube or Spotify link?
No. The page analyses files on your device and does not fetch anything from other sites. Use an audio file you have, or tap the tempo with the Tap tempo page.
What happens with songs that change tempo or key?
The page assumes one steady tempo and one key for the whole file, so it reports what fits most of the song. If the song has a tempo change, cut the part you care about with Trim audio and analyse that.
Which files work, and how long can they be?
Whatever your browser can play: MP3, WAV, M4A, AAC, FLAC and Ogg are the usual ones. WMA files are not readable in any browser. Files up to 15 minutes are analysed; for a longer one, cut the part you want first.
Is my audio uploaded anywhere?
No. The file is decoded and analysed by code running in this page, and the results, including the file name in the results file, stay on your device. After your first visit and a short wait you can turn off your internet connection and it still works.
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