Drop a song in and get its tempo. No account, no upload, no waiting in a queue.
It reads the tempo of a recording: the number you would set a metronome to in order to play along. That is what you need to time stretch a sample, line up two records, set a delay in milliseconds, or know whether a loop will sit in your song.
Most tools stop at the answer. Here is the method, because knowing it tells you when to trust the number.
A confidence gate sits at the end: if the winning lag does not stand clearly above the average correlation, the tool reports no tempo rather than inventing one. Only the first 90 seconds are analysed, since tempo is a global property.
Octave errors are the honest failure mode. Half time and double time are the same grid, and no algorithm can read your intent, so the result card shows both. Anything with a moving or absent pulse is the other failure mode: rubato, ambient, speech, and live orchestral recordings. Very short clips fail too, since roughly a second and a half of audio is not enough to correlate anything, and heavily swung or half time shuffles can land on the subdivision rather than the beat you count.
No. The file is decoded and analysed by JavaScript running in your own tab. There is no server involved, no account, and no copy of your file anywhere but your machine. You can confirm it by opening your browser's network tab, or by going offline before you drop the file in.
Because both answers are mathematically correct. A pulse at 140 BPM is also a pulse at 70 BPM counted every other beat, and autocorrelation sees both. The detector folds its answer into the 70 to 180 range, which suits most popular music, so drum and bass often reports around 87 instead of 174 and slow ballads can report double. The result card shows the half and double values so you can pick the one you mean.
Anything without a steady pulse: rubato piano, ambient pads, spoken word, orchestral music with a human conductor. Also live recordings that drift, since a single number cannot describe a tempo that moves. In those cases the detector will either report nothing or report the average of something that was never constant.
For programmed music with a stable grid it usually lands on the exact integer BPM, because the peak of the autocorrelation is refined by parabolic interpolation and then snapped to the nearest whole or half number. For live material treat it as a good starting point that you confirm by ear against a metronome.
Whatever your browser can decode, which in practice means MP3, WAV, M4A or AAC, OGG, and FLAC in most current browsers. Files longer than 15 minutes are refused, and only the first 90 seconds are analysed because tempo is a global property and more audio only costs time.
Yes. The same detector runs inside Gusta Music, the free browser studio this tool comes from. Import the file there and the tempo is detected on import, so a sample you drop on the timeline is already beat matched to your song.
Gusta Music is the free browser studio these tools came out of: multitrack timeline, sampling, mic recording, and an AI copilot that edits the song with you instead of generating one for you. Your work stays yours.
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