About EarChord
A chord finder that runs entirely inside your browser, so it can be free and unlimited without anyone paying for it in bandwidth.
What it is
EarChord takes an audio file you already have and tells you the chords in it, the key and the tempo. There is no account, no daily limit and no upload step: your browser decodes the file and the analysis runs on your own processor, in a Web Worker, in the tab you already have open.
There is also a Chrome extension that does the same thing for a YouTube video by reading the audio the player is already producing, rather than downloading anything.
Why it works this way
Most chord-finding sites fetch and analyse audio on their own servers. That makes a searchable catalogue possible, and it also makes every song someone runs cost the operator real money. That cost is where daily limits come from. It is not stinginess; it is arithmetic.
Doing the analysis in the browser removes the arithmetic. The thousandth track you analyse costs us the same as the first, which is nothing at all, so there is no reason to count them and no reason to ask who you are. The privacy property most people notice first - that your recordings never leave your machine - is a consequence of that decision rather than the reason for it, but it is the part we would defend hardest.
How the analysis is done
Classical signal processing, about three hundred lines of TypeScript, no machine learning and no third-party audio library. The audio is turned into a chromagram - how much of each of the twelve pitch classes is sounding at each moment - and each frame is matched against twenty-four major and minor triad templates. The key comes from the Krumhansl-Schmuckler profiles and the tempo from the onset envelope.
This is not the most accurate approach available. A neural network would read more chords and read them better. It would also be too large to run in a browser tab, which would mean server inference, which would mean a bill, which would mean a daily limit. We picked the constraint we could keep.
What it deliberately does not do
- It does not upload your audio, ever. There is no code path that would.
- It does not fetch YouTube or Spotify audio on a server.
- It does not report sevenths, suspensions or inversions - only major and minor triads.
- It does not keep an account, a history or a playlist, because it keeps nothing.
How it is paid for
Right now it is not: hosting a set of static pages costs almost nothing, and the analysis runs on your hardware rather than ours. In time the site will likely carry advertising and affiliate links to gear and courses. If that happens it will be on the page, never in front of the analyser, and it will not turn into a reason to meter how many songs you can run.
Who builds it
EarChord is a small independent project, not a company with a sales team. Bug reports, wrong-chord reports and feature requests all reach a person who can act on them - see thecontact page.
Last updated 26 August 2026