Guitar Tuner

What the Online Guitar Tuner Does

The Guitar Tuner listens through your device microphone, detects the pitch of the string you play, and shows how close it is to the target note. The display reports the detected frequency in hertz, a cents offset from the correct pitch, and a needle that swings between flat and sharp. When the string is within five cents of the target, the needle turns green and the status reads In Tune. Audio is analysed entirely in your browser with the Web Audio API; nothing is recorded or uploaded.

How to Use the Tuner

1. Pick a tuning preset. Standard tuning E2 A2 D3 G3 B3 E4 is selected by default.
2. Press Start Tuner and allow microphone access when the browser asks.
3. Pluck one string at a time and let it ring for a moment.
4. Watch the needle and cents reading. Negative cents mean the string is flat, positive means sharp.
5. Turn the tuning peg slowly until the status turns green and reads In Tune.
6. Press Stop Tuner when you are finished to release the microphone.

Standard Tuning Reference

These are the target frequencies for standard tuning, measured from the thickest string to the thinnest:

Alternate Tunings Supported

Besides standard tuning, the tool includes Drop D, Half Step Down, Open G, Open D, and DADGAD. Drop D lowers only the sixth string to D2, which gives a heavier one-finger power chord on the bottom strings. Open G and Open D tune the guitar to a full chord so a single strum sounds major. DADGAD is a popular modal tuning for folk and fingerstyle players. Half Step Down shifts every string down one semitone, which many singers use to match their vocal range.

How Browser Pitch Detection Works

When you grant microphone access, the browser captures the guitar signal as a stream of digital samples. The tuner runs an autocorrelation analysis on a short window of those samples. Autocorrelation compares the signal with time shifted copies of itself; the time shift that produces the strongest match is the period of the waveform, and the inverse of that period is the fundamental frequency. The detected frequency is then compared with the target frequency of each string using the cents formula, where 100 cents equals one semitone. This is why the display can show a precise offset such as 12 cents sharp instead of only the nearest note name. All of this happens locally in JavaScript, so the tuner works without sending any audio to a server.

Tips for Accurate Tuning

• Pluck close to the microphone or use your phone's built in mic at arm's length.
• Let each note ring for one to two seconds so the analysis has a stable signal.
• Tune up to the note from below. If you overshoot and the string is sharp, loosen it slightly below the target and bring it back up.
• Mute the other strings with your palm or fretting hand while tuning one string.
• Stretch new strings gently and retune, since fresh strings drift as they settle.

Related Tools

Keep time with the BPM Tap Tempo tool, generate reference pitches with the Tone Generator, and look up finger positions with the Guitar Chord Generator. If you are choosing strings or tuning down, the Guitar String Tension Calculator shows how tuning and gauge affect string tension.