Tuner
Tune a guitar, bass, ukulele or violin through your microphone. The audio is analysed on your device and never recorded or sent anywhere.
Table of contents
How to tune an instrument with your microphone
- 1
Allow the microphone
The browser will ask once. Nothing is recorded and nothing is sent — the audio is analysed frame by frame on your own device and thrown away.
- 2
Pick your instrument, or stay chromatic
Choosing a tuning tells the tuner which string you are reaching for, so a badly flat low E still reads as the sixth string rather than as the note it currently happens to be.
- 3
Play one string at a time
A single ringing note, not a chord. Pitch detection needs one fundamental to lock on to; strummed chords give it several and it will pick one of them.
- 4
Turn until the needle centres
Green means within five cents, which is closer than anyone can hear on a single note. Tune up to the pitch rather than down to it — coming from below leaves the string more stable.
What the cents number actually means
A semitone — one fret, one piano key — is divided into a hundred cents. So the number on the meter is how far you are from the note as a fraction of the smallest step in Western music: fifty cents is exactly halfway to the next note, and past that the tuner will start naming that note instead.
Five cents is the working definition of in tune here. On a single sustained note most people cannot reliably hear a difference below about five cents, and a guitar cannot hold better than that anyway — pressing a string to a fret bends it sharp, and how hard you press changes the number. Chasing zero on the display is chasing a precision the instrument does not have.
Beating between two notes is a different matter: two strings a couple of cents apart produce a slow wobble that is very audible even though neither note sounds wrong alone. That is why a guitar tuned string-by-string to a perfect tuner can still sound slightly off with itself, and why players make small adjustments by ear afterwards.
How it hears you
A plucked string does not produce one frequency. It produces a fundamental plus a stack of harmonics above it, and on a guitar's low strings the first harmonic is frequently louder than the fundamental itself. That is the trap in pitch detection: the obvious approach finds the strongest repetition in the signal and confidently reports a note an octave too high.
This one measures how well the signal matches a delayed copy of itself, divided by its own energy at that delay, and then takes the first candidate that clears a threshold rather than the strongest one. Dividing out the energy stops a loud harmonic dominating; taking the first peak stops it winning on a technicality. The result is then interpolated between samples, because without that step the reading would jump in steps of nearly a fifth of a semitone down at low E.
The microphone is also asked for raw audio specifically: echo cancellation, noise suppression and automatic gain control are all switched off. They are tuned for speech, and each of them does something a tuner cannot tolerate — gating quiet sustained tones, reshaping harmonics, or pumping the level so the note appears to move.
Frequently asked questions
No. The browser hands the page a live stream of samples, the page measures the pitch of each short window and discards it. Nothing is stored, nothing is buffered to disk, and nothing is uploaded. You can open the network panel and watch it stay silent while you tune, or load the page and disconnect from the internet first.
Because that is the only way to hear the string. There is no way to detect pitch without audio, and the browser will not give a page audio without asking you first. If you would rather not, the string frequencies are listed on the page and you can tune by ear against another instrument.
Within a cent or two under normal conditions, which is finer than the ear can resolve on a single sustained note. Two things set the floor: the sample rate your device uses, and how cleanly the string rings. A note that is buzzing, damped or already fading gives the detector less to work with, and the reading gets noisier as it decays.
Usually because the string is more than half a semitone out, in which case the nearest note genuinely is the next one along. That is exactly why picking a tuning helps: with an instrument selected, the tuner measures against the string you are aiming at, so a low E tuned a semitone sharp reads as 100 cents sharp on the sixth string rather than as a perfectly in-tune F.
No, and no tuner can. Pitch detection works by finding one repeating period in the signal; a chord contains several at once, and whichever is strongest wins. Play one string at a time and let it ring.
Concert pitch is A4 = 440 Hz and that is the default, but it is a convention rather than a law. Many European orchestras tune to 442 or 443 for a brighter sound, and baroque ensembles commonly use 415 — almost exactly a semitone below. Set it to match whatever you are playing with, and every string retunes around it.
Low notes are the hard case. A low E repeats only about 82 times a second, so a reading needs a longer slice of audio, and the fundamental on a plucked bass string is often quieter than the harmonic above it. This tuner uses a method that divides out the signal's own energy specifically to avoid reporting that harmonic instead — but a dull or dying string still gives it less to work with. Pluck nearer the bridge and let it ring.
Yes, in any modern mobile browser, using the phone's own microphone. Keep the phone within a metre or so and away from anything humming. It works offline too once the page has loaded.
Up. Tuning pegs and strings have slack in them, and arriving at the pitch from below leaves the winding under tension where it will stay. Coming down to the note leaves it loose enough to creep flat again over the next few minutes. If you overshoot, go back below and come up again.
No. No sign-up, no app to install, no ads, and nothing recorded. It is MIT licensed and the pitch detection is a hundred or so lines you can read in the repository — which is rather the point for a tool that asks for your microphone.
The Zeal Promise
Non-negotiable, on every tool we ship.
- No sign-up — ever
- No watermarks on any output
- No ads near the download button
- Works fully on mobile
- Privacy-first: processing stays in your browser
- Open source (MIT) — audit it, contribute, self-host
- Zero runtime dependencies in tool logic