Question 1

Can I analyse my whole library in one go?

Accepted Answer

Up to 100 tracks per run, and you can drop a folder instead of picking files — it is walked for you and only the audio inside is queued. They are analysed one after another, so the tab never holds two decoded tracks at once, and a running count with a time estimate tells you where it has got to. Pause it if you need the machine back, or stop it: everything already measured stays on screen.

Question 2

Which tags does it write, and what reads them?

Accepted Answer

The tempo goes into the ID3v2 frame TBPM as a whole number and the key into TKEY. Those are the two fields most DJ software reads, but applications differ in what they do with them: some import the values, others re-analyse the track themselves and prefer their own result, so it is worth checking your analysis settings if an imported value does not appear. A file whose tag uses unsynchronisation or compressed frames is reported and left alone rather than rewritten.

Question 3

Does tagging change my audio?

Accepted Answer

No. Only the tag block at the very start of the file is rewritten; every audio byte is copied across untouched, and an old ID3v1 trailer at the end of the file is left exactly as it was. The file's overall checksum does change, because the tag changed — to check the audio itself, compare the duration, or hash only the decoded stream, for example with ffmpeg -i track.mp3 -f md5 -, which gives the same value before and after.

Question 4

Why MP3 only for the tags?

Accepted Answer

Because MP3 is the one container where the result can be guaranteed. FLAC, M4A/MP4 and Ogg each keep their metadata in a completely different structure, and a half-finished writer for three more formats is how a tool starts damaging people's libraries. Those files are still analysed exactly as before — only the write-back is held back.

Question 5

How accurate is it?

Accepted Answer

On our own synthetic test set — metronome click tracks generated inside the unit tests at 90, 120, 128 and 174 BPM — it returns the exact tempo to within 0.1 BPM. That measures the maths, not real music. In practice the reading is dependable for anything with a steady beat and much less so for rubato playing, orchestral music, ambient, and tracks that change tempo part-way through.

Question 6

Why does it show half-time and double-time?

Accepted Answer

Because the tempo octave is genuinely ambiguous. A drum-and-bass track is 174 BPM to a DJ and 87 to a dancer; a slow hip-hop beat is 85 or 170 depending on whether you count the hi-hats. The tool picks the reading that fits the music best and shows the other two so you can take the one your project needs.

Question 7

Is this BPM finder really free?

Accepted Answer

Yes. No signup, no credit card, no daily quota and no watermark. The analysis runs on your own processor, so there is no server bill for us to pass on to you.

Question 8

Is my song uploaded anywhere?

Accepted Answer

No. The file is read straight from your disk and decoded by the browser's own audio engine. You can prove it: open DevTools, switch to the Network panel, then analyse a track — you will not see your file being sent anywhere. Turning off your Wi-Fi after the page loads works just as well.

Question 9

Which file formats can it read?

Accepted Answer

MP3, WAV, M4A, AAC, OGG, Opus and FLAC, plus the audio track of an MP4 or WebM. Whatever your browser can play, this can analyse — Safari and Chrome differ slightly on exotic codecs, and an unreadable file says so instead of failing silently.

Question 10

Does it work on a phone?

Accepted Answer

Yes, in any modern mobile browser. A three-minute track takes a couple of seconds on a recent phone. Very large files are the limit rather than the tool: a phone has less memory than a laptop, so a 200 MB FLAC may be too much for an older device.

BPM Finder

How to Find and Tag the BPM of Your Tracks

Drop a folder, or up to 100 files

Let the queue run

Write it back into the tags

Audio Converter

Audio to MIDI

Audio Trimmer

Noise Remover

Ringtone Maker

Tap BPM

Song Key Finder

Video to MP3

MP3 to MP4

Frequently Asked Questions

Can I analyse my whole library in one go?

Which tags does it write, and what reads them?

Does tagging change my audio?

Why MP3 only for the tags?

How accurate is it?

Why does it show half-time and double-time?

Is this BPM finder really free?

Is my song uploaded anywhere?

Which file formats can it read?

Does it work on a phone?

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