Online guitar tuner

How to tune a guitar with this page

Pick your tuning, allow the microphone when the browser asks, and play one string at a time. The readout names the note it hears, marks the string of your tuning it is closest to, and shows the distance in cents: left of centre is flat, right is sharp. When the needle sits in the middle band the string is within three cents, which is closer than anyone can hear.

Play the string firmly and let it ring rather than holding a chord. A tuner reads one note at a time, so two strings sounding together will pull the reading between them. Somewhere quiet helps, and so does keeping the phone or laptop within an arm's length of the instrument.

Tune up to the note rather than down onto it. Coming from below keeps the tension on the tuning peg loaded in one direction, which is what stops a freshly tuned string drifting flat again over the next few minutes.

What the reading actually measures

A cent is a hundredth of a semitone. Naming the note is the easy half of tuning; the hard half is the last few cents, and that is the number this page puts in front of you rather than hiding behind a green light. Reference pitch is A4 = 440 Hz, and every string target is derived from it by equal temperament.

The pitch is found from the period of the waveform, using the normalised square difference function, not from the tallest peak in the spectrum. That distinction matters on a low E: phone microphones and small laptop speakers roll off below about 100 Hz, so a bottom string often arrives with its second harmonic louder than its fundamental. A tuner that reads the spectrum then reports the octave above, confidently. Reading the period survives a missing fundamental, which is why the low strings behave here.

When nothing periodic is in front of the microphone the page says it is listening instead of naming a note. Room noise has energy everywhere and a pitch nowhere, and a tuner that names a note anyway is worse than one that admits it cannot hear you.

Where a browser tuner struggles

Loud rooms, an amplifier in the same room, and heavy distortion are the hard cases. Distortion in particular adds harmonics that were never in the string, and it is the one situation where plugging into a dedicated pedal tuner is genuinely better. Tune clean, then turn the gain back up.

Very quiet playing is the other failure. The detector has a level floor so that a silent room cannot produce a reading, and a string plucked gently three metres away can fall under it. Move closer and play harder rather than turning up the system input gain, which raises the noise with the signal.