What this online tuner is
This page is an instrument tuner that listens through your microphone, works out which note you are playing and shows how close it is to being in tune. It also plays reference tones for guitar, ukulele and violin strings, so you can tune by ear when you have no microphone. It runs in your browser, with nothing to install and no account.
The audio from your microphone is analyzed on your own device as it arrives. It is not recorded, saved or sent anywhere, and the microphone is switched off when you press Stop, switch to another tab or leave the page.
How the tuner finds the pitch
A musical note is a repeating sound wave, and its pitch is the number of repeats per second, called its frequency and measured in hertz. The tuner takes a short slice of sound from the microphone and looks for the shortest time after which the wave repeats itself. This method is called autocorrelation. Divide the sample rate by that repeat time and you have the frequency.
The frequency is then turned into a note. Western music uses equal temperament, where each semitone is the same ratio apart, and A4 is the reference, normally 440 Hz. The tuner finds the nearest note and measures how far you are from it in cents. One hundred cents make one semitone, so being 10 cents off is a small error and 50 cents is halfway to the next note.
Reading the display
The large letter and number show the nearest note, for example A4 or E2. Under it are the exact frequency and the number of cents. The needle on the meter moves from minus 50 on the left, meaning flat, to plus 50 on the right, meaning sharp. When it is within 5 cents of the center, the label shows In tune and the needle changes color.
The reading is smoothed over a few measurements so that it does not jump about. If the note stops, the display returns to a resting state after half a second. If the display shows nothing while you play, the note may be too quiet, too noisy or outside the range the tuner can follow.
Tuning a guitar
A guitar in standard tuning has six strings. From the thickest to the thinnest they are E2, A2, D3, G3, B3 and E4. Press Start microphone, pluck the lowest string alone and let it ring. Raise or lower the string with the tuning peg until the needle settles at the center and the label says In tune, then move to the next string.
It is easier to tune up to a note than down. If a string is too sharp, loosen it a little below the note and then tighten it back up to the pitch, which helps the string stay in tune. Tune all six strings, then check the first again, because changing the tension of one string can shift the others slightly.
Tuning a ukulele or a violin
A standard ukulele has four strings tuned G4, C4, E4 and A4. The G string is a high one, called re-entrant tuning, which gives the ukulele its bright, jangly sound. A violin is tuned in fifths: G3, D4, A4 and E5. Violin strings are usually tuned with the pegs for a large change and with the small fine tuners near the tailpiece for the last few cents.
In each case, play one string at a time, let it sound for a moment, and watch the needle. The Reference tones section has a button for every string of these three instruments, which is helpful if you want to hear the target pitch first and match it by ear.
Tips for accurate readings
- Use a quiet room. Other sounds, such as fans, voices or music, confuse the detection.
- Play one note at a time. Chords and strummed strings contain several pitches, and the tuner follows only one.
- Let the note ring. The first instant of a plucked note is noisy, and the pitch settles a moment later.
- Keep the microphone close. Hold the instrument within about half a meter of your device, but not so close that the sound distorts.
- Do not play the reference tone and listen at once. The speaker sound would be picked up by the microphone and read as a note.
Reference pitch and tone buttons
The Reference A4 slider sets the pitch that the tuner treats as A4, from 430 to 450 Hz. The standard is 440, and nearly all modern instruments and recordings use it. Some ensembles use 442, and some players of early music use lower values, so the slider lets you match a group or a piano that is tuned differently.
Press a string button to hear a steady sine tone at that pitch, and press it again to stop. Only one tone sounds at a time, and changing to another string stops the first.
Microphone and privacy
Your browser always asks permission before a page can use the microphone, and it shows an indicator while the microphone is on. The tuner starts only when you press the button. If you refuse, nothing is lost, and you can still use the reference tones. If you refused by mistake, open your browser's site settings for this page, allow the microphone and press the button again.
The tuner requests the raw microphone signal with echo cancellation, noise suppression and automatic gain turned off, since these features are designed for speech and can disturb pitch. The signal goes to the analysis code only and is not played through the speakers, so there is no feedback.
What an online tuner is good for
An online tuner is handy when you do not own a clip-on tuner, when you want to check your tuning quickly before a session, or when you are learning to hear pitch. Singers can use it to see how close they are to a note. Combine it with the virtual guitar and the virtual ukulele to hear the notes before you tune, and use the online metronome to keep time while you practice.
Online tuner versus a clip-on or pedal tuner
A clip-on tuner senses the vibration of the instrument through contact, so it ignores room noise and works well on stage. A pedal or rack tuner takes a signal straight from an electric instrument. Both are fast and very reliable in noisy places.
The online tuner relies on your device microphone, so it is best in a quiet room. It is free, needs no equipment and shows frequency and cents in detail. For a loud environment or performance, a dedicated tuner is still the safer choice.
Limitations of this version
- It follows a single note at a time, between about 60 Hz and 1,200 Hz. Very low bass notes and very high notes are outside that range.
- Accuracy depends on your microphone and the room. It was checked here with generated test tones, and real instruments, which contain overtones and noise, can read less steadily.
- Chords, noisy rooms and fast passages are not tracked reliably.
- There is no support for alternate tunings. The reference tones cover only standard tunings of a guitar, a ukulele and a violin.
- The microphone needs a secure (HTTPS) page and your permission.
Common problems and how to fix them
- The browser did not ask for permission. It may have been blocked before. Open the site settings for this page, allow the microphone and try again. The page must also be on HTTPS.
- Nothing is detected. Play louder, move closer, and check that the right microphone is selected in your device settings.
- The note jumps between values. Let the note ring, reduce background noise and play one string at a time.
- The note is off by an octave. This can happen with very low or very quiet notes. Pluck again more firmly.
- No sound from the tone buttons. Press a string button after interacting with the page, then check your volume, the tab's mute icon and, on an iPhone, the silent switch.