Online Instrument Tuner — Guitar, Bass, Ukulele & Violin
Chromatic tuner with cent-accurate deviation, presets for common instruments and an adjustable A4 reference. Audio is processed in the page and never recorded.
Free Online String Instrument Tuner
This free browser-based string instrument tuner detects the pitch of your instrument in real time using your device's microphone and shows you exactly how sharp or flat you are in cents. It supports guitar (standard E A D G B E tuning), drop D guitar, 4-string bass guitar (E A D G), ukulele (G C E A), violin (G D A E), and cello (C G D A). All pitch detection runs entirely in your browser via the Web Audio API — no audio is ever uploaded or sent to a server. The visual meter shows cents deviation (±50¢) with colour-coded zones: green for in-tune (±5¢), amber for close (±20¢), and red for out of tune. A reference table highlights the nearest string as you play, making it easy to tune string by string.
Standard tunings
| Instrument | Strings, low to high | Note |
|---|---|---|
| Guitar — standard | E2 A2 D3 G3 B3 E4 | The B string is the odd interval: a major third, where the rest are fourths |
| Guitar — drop D | D2 A2 D3 G3 B3 E4 | Low string down a tone; lets a power chord be fretted with one finger |
| Guitar — half step down | E♭2 A♭2 D♭3 G♭3 B♭3 E♭4 | Common for vocal range and slightly slacker feel |
| Bass — 4 string | E1 A1 D2 G2 | An octave below the guitar’s lowest four |
| Bass — 5 string | B0 E1 A1 D2 G2 | B0 is about 31 Hz — below what most laptop microphones capture well |
| Ukulele — soprano/concert | G4 C4 E4 A4 | Re-entrant: the G is higher than the C, not lower |
| Violin | G3 D4 A4 E5 | Tuned in fifths |
| Cello | C2 G2 D3 A3 | Fifths, an octave below the viola |
| Mandolin | G3 D4 A4 E5 | Same as violin, in paired courses |
Cents, and what "in tune" means
The tuner shows deviation in cents. A cent is one hundredth of a semitone, so an octave is 1200 cents. The scale is logarithmic because pitch perception is: the same musical interval corresponds to the same frequency ratio, not the same difference in Hz.
That is why A2 to A#2 is about 6.5 Hz while A4 to A#4 is about 26 Hz — the same semitone, four times the absolute difference. Measuring tuning error in Hz would be meaningless across registers; cents are comparable everywhere.
For context: most people notice a discrepancy of about 5 cents on a sustained note played against another, and trained musicians hear 2–3 cents. Within ±5 cents is well in tune for a guitar. Chasing ±1 cent is wasted effort, because fretting pressure alone bends a note further than that.
A related point worth knowing: a guitar is never perfectly in tune. Equal temperament is a compromise that divides the octave into twelve equal ratios so that every key is equally usable and none is perfectly consonant. The major third in equal temperament is about 14 cents sharp of the pure ratio — audibly so — which is why some players deliberately tune slightly off-standard to favour the keys they play in.
When the tuner misbehaves
Reading jumps around, especially on low strings
Cause:Low notes need a long analysis window — a 41 Hz low E has a period of 24 ms, so several periods take a meaningful fraction of a second. Harmonics can also be stronger than the fundamental, and the detector locks onto the wrong one.
Fix:Play closer to the bridge for a clearer fundamental, let the note ring rather than picking repeatedly, and reduce background noise. Very low notes on a 5-string bass may exceed what a laptop microphone can capture at all.
Shows a note roughly an octave off
Cause:Octave error in pitch detection — a harmonic being read as the fundamental.
Fix:Pluck more softly. A hard attack emphasises the upper harmonics; a softer one leaves the fundamental dominant.
No microphone input at all
Cause:Permission denied, the wrong input device selected, or the page not served over HTTPS — browsers only grant microphone access on a secure origin.
Fix:Check the permission prompt and your browser’s site settings, and confirm the correct input device is chosen at the OS level.
A string will not hold its tuning
Cause:New strings stretch for the first few hours of play. Beyond that: a slipping tuning peg, a string binding in the nut slot, or ambient temperature change.
Fix:Stretch new strings deliberately by pulling gently along their length and retuning, several times. If it persists, lubricate the nut slots — binding at the nut is the most common cause on an otherwise healthy instrument.
About
The String Tuner uses your device's microphone to detect the pitch of each string as you play it and shows you how flat or sharp you are relative to the target note. It supports standard guitar (EADGBE), bass (EADG), ukulele (GCEA), violin (GDAE), and cello (CGDA) tunings, plus chromatic tuning for any note.
How to use
- 1 Click Allow when your browser asks for microphone access.
- 2 Select your instrument and tuning from the options.
- 3 Play a string — the tuner shows the detected pitch and how close you are.
- 4 The needle moves left (flat) or right (sharp) relative to the target note.
- 5 Tune the string until the needle is centred on green.
- Does the string tuner work without installing an app?
- Yes. The tuner runs entirely in your browser using the Web Audio API and the getUserMedia microphone API. No app download or installation is needed — just grant microphone permission when prompted and start tuning. It works on mobile browsers (Chrome, Safari) as well as desktop.
- What is standard guitar tuning?
- Standard guitar tuning is E2-A2-D3-G3-B3-E4 from the thickest string (6th) to the thinnest (1st). The reference pitch is A4 = 440 Hz. The tuner detects your string's pitch and compares it to the nearest standard note, showing how many cents flat or sharp you are. A cent is 1/100th of a semitone.
- What is a chromatic tuner and when should I use it?
- A chromatic tuner detects any pitch and shows the nearest note in the chromatic scale, regardless of instrument. Use it for alternate tunings (drop D, open G, DADGAD), unusual instruments, or any situation where you need to tune to a specific note that is not in a preset instrument tuning. The standard instrument tunings are presets built on top of the same chromatic detection engine.
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