Guitar tuner
Tune your guitar online with your microphone. Standard, Drop D, Open G, Open D, DADGAD, and half-step-down tunings with a cents readout for every string. Free, no signup, audio never leaves your browser.
How to use the guitar tuner
- Pick your tuning from the dropdown and set the A4 reference if you do not tune to 440 Hz.
- Click Start tuner and allow microphone access when your browser asks.
- Play one open string and let it ring. The tuner shows the nearest note, how many cents you are off, and highlights the closest string.
- Adjust the peg until the needle sits in the green center within 5 cents, then mute that string and move to the next.
How the tuning math works
The tuner estimates pitch with normalized autocorrelation: it compares the microphone signal against copies of itself shifted by different time lags and picks the lag where the two match best. That lag is the vibration period, and dividing the sample rate by it gives the frequency in hertz. A parabolic fit around the best lag refines the period between samples. The frequency is mapped to the nearest semitone of equal temperament, where each semitone is the 12th root of two above the next lower one, and the cents readout is 1200 times the base-2 logarithm of the ratio between what you played and the target.
Frequently asked questions
How does the tuner hear my guitar?
Your microphone feeds the Web Audio API, which estimates the string's period with autocorrelation and converts it to a frequency. The tuner then maps that frequency to the nearest note in equal temperament using your A4 reference, 440 Hz by default, and reports the difference in cents.
Is my audio uploaded anywhere?
No. Pitch detection runs locally in your browser. Nothing is recorded, uploaded, or stored, and the microphone stream stops when you press Stop tuner or leave the page.
What does the cents readout mean?
A cent is one hundredth of a semitone. Within about 5 cents of the target a string sounds in tune; most listeners stop hearing deviation around 10 cents. A negative reading means the string is flat, so tighten the peg; a positive reading means it is sharp, so loosen it.
Which tunings are included?
Standard E (E2-A2-D3-G3-B3-E4), Drop D, Half step down, Open G, Open D, and DADGAD, each listed from the low string to the high string. The A4 reference is adjustable between 415 and 466 Hz for players who tune to a different pitch standard.
Why does the note jump around while I play?
Background noise, several strings ringing at once, or a dying battery in an acoustic pickup all confuse pitch detection. Play one open string at a time, let it ring for a second, and mute the others. The tuner needs a clean, steady tone to settle on a note.