Tool

Browser tuner

By Band Tuning editorial · Facts checked 15 September 2026

Pick your instrument, play the reference tone or let the microphone read your pitch. Notes are named against A4 = 440 Hz in equal temperament, the same standard as every instrument page here.

What it needs. A browser with the Web Audio API (current Chrome, Edge, Firefox and Safari have it). The reference tones need nothing else. The pitch readout needs a microphone and your permission when the browser asks; the sound is analysed in the page and never sent anywhere, and if you refuse or have no microphone the reference tones still play.

How the readout works

The page opens the microphone through getUserMedia with the browser's echo cancellation, noise suppression and automatic gain switched off, and feeds it to an AnalyserNode that hands over 8,192 samples at a time. The detector is an autocorrelation: it multiplies the signal by a delayed copy of itself for every delay from the period of 2,500 Hz down to the period of 35 Hz, averaged over the samples that overlap so long delays are not penalised, takes the first peak after the correlation's first dip that stands at least nine tenths as high as the strongest peak (the period, rather than a multiple of it), and refines the delay by fitting a parabola through the three points around that peak. The sample rate divided by that delay is the frequency. Below a small loudness threshold nothing is reported, so the needle rests between notes instead of chasing room noise.

The nearest note is round(69 + 12 × log2(f / 440)) as a MIDI number, and the cents off are 1200 × log2(f / f_note), where f_note is that note's equal-tempered frequency. A green band means within five cents. Brass players: the readout hears the sounding pitch, so the "written" line under the note name is the note you read on your part for what the tuner heard, using the instrument's transposition from its reference page.

Limits worth knowing: the detector expects one note at a time and a clear fundamental; a very quiet low note on a tuba or bass clarinet, a noisy room, or two instruments at once can make it jump an octave or between neighbouring notes. Hold the note steady and the readout settles.