Online Guitar Tuner

A free online guitar tuner built for the absolute beginner: someone holding a borrowed guitar who doesn’t know which string is which, which peg to turn, or which way. Open tuner.klokie.com, tap start, allow the microphone, and pluck — the tuner names the string, highlights the right peg on a headstock diagram, and tells you whether the pitch needs to come up or down.

Under the hood: real-time pitch detection with the McLeod Pitch Method (the pitchy library) reading a plain Web Audio AnalyserNode — no WebAssembly, no audio worklets, because a tuner doesn’t need them. All audio is processed locally in the browser and never uploaded. Seven tunings at launch (standard, drop D, drop C, DADGAD, open G, half step and whole step down), each a static Astro page built from one shared data model.

The interesting constraints were product, not DSP: guidance never claims a rotation direction (wrong advice can snap a string on exactly the user this is for), auto string-detection refuses to guess beyond ±2 semitones, and the whole beginner flow — including microphone-denied fallbacks — is covered by end-to-end tests that feed synthesized guitar tones into a fake browser microphone.

Read the build story: From a two-year-old todo to a live product in one day.