Upload a track and this free key and BPM finder detects its tempo and musical key automatically. The analysis runs entirely in your browser — your audio file is never uploaded anywhere.
Runs entirely in your browser. Your file is never uploaded anywhere.
How to find the key and BPM of a song
- Click the upload area, or drag an audio file straight onto it.
- The tool analyses the track right in your browser — nothing is sent to a server.
- Read the detected BPM and the estimated musical key.
Your audio never leaves your device
Most online key finders upload your file to their server, analyse it there, and send the result back. That means handing an unreleased track, a client’s stems or a private demo to a third party.
This tool does not work that way. The file is decoded and analysed locally in your browser using the Web Audio API. Nothing is transmitted, nothing is stored, and nothing is retained after you close the tab. You can disconnect from the internet after the page loads and the analysis still runs. That makes it safe for unreleased material.
Why knowing the key and BPM matters
The key tells you which notes and chords will sound in tune with a track, and the BPM tells you its tempo. Together they’re essential for DJing, remixing, mashups and sampling. If you want to layer an acappella over an instrumental, both need to be in a compatible key and at the same tempo, or the mix will clash. This song key finder gives you both numbers in seconds.
What you can do with the key and BPM
- Harmonic mixing — match songs in compatible keys for smooth DJ transitions.
- Remixing and mashups — line up acappellas and instrumentals that share a key and tempo.
- Sampling — pitch and time-stretch a sample to fit the key and BPM of your project.
- Covers and practice — find the key of a song so you can play or transpose it.
Which keys mix well together
Once you know a track’s key, harmonic mixing is straightforward. Two songs blend smoothly when their keys are closely related, which means any of these:
- The same key. Always safe.
- The relative minor or major. C major and A minor share every note, so they mix seamlessly.
- One step around the circle of fifths. C major sits comfortably next to G major and F major.
Jumping to an unrelated key — C major straight into F# major, for example — creates a clash unless you use it deliberately as a lift.
How accurate is automatic key and BPM detection?
BPM detection is usually very reliable for music with a clear, steady beat. Key detection is an estimate: it analyses the harmonic content of the track and picks the most likely key. It works best on clean, tonal music and can be less certain on busy, heavily processed or atonal tracks. Treat the key as a strong starting point, then confirm by ear.
Two common failure modes are worth knowing. A detected key that is a relative major or minor of the true key (A minor reported instead of C major) is a near-miss and still mixes fine. A tempo reported at double or half the real value is common in half-time genres such as dubstep, where 140 BPM is often felt as 70.
Frequently asked questions
How do I find the key of a song?
Upload the audio file and this key finder analyses its harmonic content to estimate the musical key, along with the tempo in BPM.
Is my audio file uploaded anywhere?
No. The analysis runs entirely in your browser using the Web Audio API. Your file never leaves your device, nothing is stored, and nothing is retained after you close the tab. It is safe to use with unreleased music.
How accurate is the key detection?
Key detection is an estimate. It works well on clear, tonal music but can be less certain on very busy or atonal tracks. If the result is the relative major or minor of what you expected, that is a common near-miss and the two keys still mix well together.
What audio formats are supported?
Common formats such as MP3, WAV and M4A work in most modern browsers.
Why is the detected BPM double or half what I expected?
This happens in genres with a half-time feel. Dubstep at 140 BPM is often felt as 70, and drum and bass at 174 can register as 87. Both readings describe the same groove, so pick whichever matches how you count the track.
Can I find the BPM by tapping instead?
Yes — if you’d rather tap along to the beat, use our BPM Tapper.
Once you know the key, look up its notes and compatible chords in the chord and scale finder, or practise to the tempo with the online metronome. See all our free music tools.