Free Online Instrument Tuner

Chromatic tuner that uses your microphone for real-time pitch detection. Tune guitar, bass, ukulele, violin, or any instrument. See cents deviation on a visual meter with color-coded accuracy feedback.

12 min read

How This Tuner Compares

This chromatic tuner provides more tuning presets and visualization options than most online alternatives, while keeping the interface clean and responsive.

How to Tune Your Guitar

This video walks through the process of tuning each guitar string to standard pitch. Use the tuner above while watching to practice the technique in real time.

Complete Guide to the Online Chromatic Tuner

Tuning an instrument accurately is essential for good sound. Whether you play guitar, bass, ukulele, violin, or any other pitched instrument, being in tune means your notes match the frequencies that other musicians and recordings expect. This online tuner uses your device microphone and the Web Audio API to detect pitch in real time, showing you exactly which note you are playing and how many cents sharp or flat you are from the target.

The tuner works by capturing audio from your microphone using the getUserMedia API. The raw audio data is fed into an analyser node, which provides time-domain data for pitch detection. The autocorrelation algorithm compares the waveform against shifted versions of itself to find the fundamental period, which directly corresponds to the frequency of the note. This method is reliable and works well for monophonic signals (one note at a time).

Understanding Cents

A cent is one hundredth of a semitone. There are 100 cents between any two adjacent notes (for example, between C and C#). When the tuner shows 0 cents, your note is exactly on pitch. Positive cents mean you are sharp (too high), and negative cents mean you are flat (too low). Most musicians consider a note to be acceptably in tune when it falls within plus or minus 5 cents of the target. The color-coded display makes this easy to see at a glance: green for in tune, yellow for close, and red for significantly off.

Reference Pitch

The reference pitch determines what frequency A4 is set to. The international standard is 440 Hz, which means the A above middle C vibrates at 440 cycles per second. All other notes are calculated from this reference using the equal temperament formula. Some musicians prefer 442 Hz, which is common in European orchestras and produces a slightly brighter overall pitch. Others prefer 432 Hz, which some describe as warmer or more natural. The custom option lets you set any reference between 400 and 480 Hz.

Tuning Presets

The tuning preset selector changes which target notes are displayed. In chromatic mode, the tuner identifies any note and shows the nearest pitch. When you select a specific instrument preset, the tuner displays the target strings with their expected notes and frequencies. This helps you focus on tuning one string at a time.

Guitar Standard (EADGBE) tunes the six strings from low E2 (82.41 Hz) through A2, D3, G3, B3, to high E4 (329.63 Hz). Drop D changes the lowest string to D2 (73.42 Hz), which gives you a heavier low end and makes power chords easier on the bottom three strings. Open G (DGDGBD) tunes the guitar so that strumming all open strings produces a G major chord, which is popular for slide guitar and blues. Open D (DADF#AD) produces a D major chord and is commonly used in folk and fingerstyle playing.

Ukulele standard tuning (GCEA) tunes four strings with the G string typically pitched higher than the C string, creating the characteristic bright ukulele sound. Bass standard (EADG) covers the four strings of a bass guitar, tuned one octave lower than the bottom four guitar strings. Violin (GDAE) tunes the four strings in fifths from G3 to E5.

The Autocorrelation Algorithm

Autocorrelation is a signal processing technique that measures how similar a signal is to a delayed copy of itself. For a periodic signal (like a musical note), the autocorrelation function peaks at delays corresponding to the period of the fundamental frequency. The algorithm implemented in this tuner analyzes the time-domain data from the Web Audio API analyser node.

The process works in several steps. First, the raw audio buffer is normalized to remove DC offset. Then, the autocorrelation is computed for a range of possible periods (corresponding to frequencies from about 50 Hz to 1500 Hz). The algorithm finds the delay at which the autocorrelation value is highest. This delay is the period of the fundamental frequency. The frequency is then calculated as the sample rate divided by the period. Parabolic interpolation refines the result for sub-sample accuracy.

This approach handles most musical instruments well because it is based on periodicity rather than spectral peaks. Instruments with strong harmonics (like guitar, where the second harmonic can be louder than the fundamental) can sometimes confuse spectral methods, but autocorrelation reliably finds the correct period regardless of the harmonic balance.

Waveform Visualization

The oscilloscope display at the top of the tuner shows the raw waveform of your microphone input in real time. A clean, repeating wave pattern indicates a steady pitch. Erratic or noisy waveforms suggest background noise or a note that is still sustaining and decaying. Watching the waveform while tuning helps you develop an intuition for what a well-tuned note looks like. A perfectly tuned open string on a guitar produces a nearly sinusoidal wave with steady amplitude.

Tips for Accurate Tuning

Tune in a quiet environment. Background noise, fans, and other instruments can interfere with pitch detection. Play one string at a time and let it ring clearly. Avoid touching other strings, which can add sympathetic vibrations. For guitar, pluck near the middle of the string for the cleanest fundamental. Tune up to the note rather than down: if you are sharp, go below the target and come back up. This helps the string settle into position and reduces slippage.

New strings stretch and go out of tune quickly. After putting on new strings, tune them, stretch them by gently pulling away from the fretboard, and retune. Repeat this process several times until the strings hold their pitch. Temperature and humidity also affect tuning. Wooden instruments expand and contract with environmental changes, so check your tuning whenever conditions change.

The reference tone generator is useful for ear training. Click a target note, listen to the pure tone, then play the corresponding string. Try to hear the difference between your string and the reference before looking at the meter. Over time, this develops your ear to the point where you can tune reasonably well without a tuner.

Equal Temperament and Alternative Tuning Systems

This tuner uses equal temperament, where each semitone has the exact same frequency ratio (the twelfth root of 2, approximately 1.05946). This system allows you to play in any key with the same interval relationships. However, it is a compromise: pure intervals like the perfect fifth and major third are slightly different from their mathematically pure ratios. Just intonation uses pure ratios and sounds smoother for static chords but makes it impossible to modulate freely between keys. Pythagorean tuning optimizes fifths at the expense of thirds. For practical purposes, equal temperament is the standard that all modern instruments and this tuner use.

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