BPM and Key Finder: tempo and key of any song, free
Tempo and key, read from the file itself and never sent anywhere. Drop a track to find out what it is in — then set a line of it as a card if you want something to post.
Drop an audio file here
MP3, WAV, M4A, AAC, OGG, FLAC
Nothing is uploaded. The file is read and analysed in this browser.
Why it does not upload your file
Every browser already has a full audio engine in it. Decoding an MP3, filtering it down to the kick drum, and measuring the spacing of the peaks are all things it can do without help — so sending the file to a server would add a wait, a privacy question and a running cost for no gain in what comes back. That also means there is no quota here: nothing is being spent when you use it.
What the numbers mean
Tempo comes from the gaps between the loudest low-frequency moments — the kick, in most music. Those gaps are counted rather than averaged, so one missed beat does not drag the reading. Key comes from how much energy sits in each of the twelve pitch classes across the track, matched against how strongly each degree is felt in a major and a minor key. Both are measurements, not opinions, but both are read off a signal that can be genuinely ambiguous — which is why the runners-up are shown.
Frequently asked questions
- Is my file uploaded anywhere?
- No. The browser decodes and analyses the audio locally with the Web Audio API. No bytes are sent to a server, which is also why the tool costs nothing to run and has no limit on how often you use it.
- How accurate is it?
- Tempo is reliable on anything with a steady kick in common time and less so on free-time, rubato or heavily syncopated material. Key detection ranks all twenty-four keys by how well the track's pitch content fits each one, so treat the top result as the most likely rather than as a verdict.
- Why does it show half and double time?
- A beat grid at 70 BPM fits the same peaks as one at 140. Neither is wrong, and which one a musician calls the tempo depends on the genre, so both are shown instead of the tool picking for you.
- Why is a section of the track analysed rather than all of it?
- Ninety seconds from the middle. Intros often have no beat and no settled key, and reading the whole file is slower without being more certain.
- It says no steady beat was found.
- That is the honest answer for ambient, free-time or spoken material, which has no tempo to report. The tool says so rather than returning a number it cannot stand behind.