Tuner
Play a note and the tuner names it and shows how far off you are, in cents.
Press Start listening and play a note.
The string closest to what you are playing lights up, and the meter measures against that string — so a badly flat sixth string still reads as E2.
415–466 Hz. Leave it at 440 unless you are playing with an ensemble that has agreed on something else.
Tuner stopped.
Tuner idle, instrument Guitar, reference pitch 440 Hz. Note none, string none, frequency none, none cents, none.
Nothing is recorded or uploaded — the audio never leaves this page. The link in your address bar carries the instrument and the reference pitch.
What the numbers mean. Play one note and the tuner shows which note it is and how far off you are in cents. A cent is a hundredth of a semitone, so there are 1200 of them in an octave — the meter here runs 50 cents either way, which is half a semitone, because past that you are closer to the next note and the tuner says so instead. Anything inside 5 cents counts as in tune. That is roughly the point at which a trained ear stops hearing the beating between two notes, and it is about as tight as a fretted instrument will hold for the length of a song anyway.
Flat means turn it up, sharp means turn it down. The needle sits left of centre when the note is flat — below where it should be — and right of centre when it is sharp. Tune up to the note wherever you can: bring the string below pitch and raise it into place, so the tension is pulling against the peg rather than settling back through it. A string tuned down into position tends to drift sharp again as it settles.
Instrument presets and why they help. Chromatic mode names whichever note is nearest, which is what you want for a keyboard, a wind instrument, or a voice. On a string preset the tuner instead measures against the nearest string of that instrument, and that changes the answer in exactly the case where it matters: a sixth string a whole tone flat reads as "E2, 200 cents flat" rather than "D2, in tune". The second is perfectly true and tells you nothing about which peg to turn. The presets cover standard guitar, drop D, four-string bass, ukulele in the usual reentrant tuning with its high G, and violin.
Reference pitch. Almost everything is tuned to A4 = 440 Hz, and if you do not know otherwise that is the number you want. It is adjustable from 415 to 466 Hz because two situations genuinely need it: period instruments and ensembles playing Baroque repertoire often use 415, which is almost exactly a semitone down, and some orchestras tune to 442 or 443 for a brighter sound. Changing it moves every note the tuner knows about by the same ratio, so the intervals between them are untouched.
How the pitch is worked out. The tuner takes short slices of what the microphone hears and runs the YIN algorithm over each one, which looks for the shortest delay at which the waveform most nearly repeats itself. That delay is the period; one divided by it is the frequency. The reason it is YIN rather than plain autocorrelation is the octave problem: a plucked string has a strong second harmonic, and the simple version matches just as well at half the period as at the whole one, so it reports the note an octave up. YIN normalises the comparison in a way that makes the true period the first one it finds. The result is then fitted to a parabola between neighbouring samples, without which the reading would jump in steps of about 20 cents at the top of a violin's range.
Getting a clean reading. Play one note at a time, reasonably firmly, and let it ring — a chord gives the tuner several pitches to choose between, and it will pick one and look confident about it. Get close to the microphone in a noisy room. Pluck near the bridge rather than over the soundhole if the reading wanders, because that puts more energy into the fundamental. And if the needle drifts sharp for a moment right after the pluck, that is real: a string is briefly sharp while the initial attack decays, which is why experienced players tune to the note a second or so after it starts.
What it does not do. Nothing is recorded, stored or uploaded — the audio is analysed in the page and thrown away frame by frame, and stopping the tuner releases the microphone. There is no account, no analytics and no tracking of any kind. The instrument and reference pitch are saved in this browser and carried in the address bar so you can send someone a link, and that is the only thing that leaves the page.
Why does it need microphone access?
Because it works out the pitch of what it hears. The browser asks you once and the answer is yours to change at any time from the padlock or camera icon in the address bar. The audio is analysed inside the page and never leaves it — there is no server involved, and stopping the tuner releases the microphone straight away.
What is a cent?
A hundredth of a semitone, so 1200 to the octave. It is the useful unit for tuning because it means the same thing everywhere: five cents is five cents whether you are tuning a bass low E or a violin E string, while five hertz is a big error on one and an inaudible one on the other.
How close is close enough?
This tuner calls anything within 5 cents in tune. For most playing that is plenty — a fretted instrument will not hold better than that through a song, and temperature alone moves a guitar by more. Orchestral players and anyone recording will want the needle dead centre.
Why does the note name jump around when I play a chord?
Because a chord is several notes and the tuner reports one pitch. It is not confused so much as answering a question you did not mean to ask. Mute the other strings and play one at a time.
It says E2 but I am nowhere near E — what is going on?
On an instrument preset the tuner measures against the nearest string rather than the nearest note, so a string a long way out still reads as the string it is. That is the useful answer, because it tells you which peg to turn. Switch to Chromatic if you want the nearest note instead.
Can I tune to something other than A = 440?
Yes — the reference pitch is adjustable from 415 to 466 Hz. 415 is the usual Baroque pitch, roughly a semitone down, and 442 or 443 is common in orchestras. Every note moves with it, so the intervals are unchanged.
Why is the low E on my bass harder to read?
Low notes need a longer slice of audio to measure, and small speakers and phone microphones deliver very little energy down there — often none at all at the fundamental. The tuner handles a missing fundamental (it reads the harmonics instead), but it still needs a clean, firm note. Play nearer the bridge and let it ring.
Does it work offline?
Yes. The whole thing runs in your browser and the site is a progressive web app, so once the page has loaded once it keeps working with no connection. Microphone permission is remembered by the browser, not by the page.
Why does it stop when I switch tabs?
Because leaving the microphone open on a page nobody is looking at is not a reasonable thing for a web page to do — your browser would keep its recording indicator lit the whole time. Come back to the tab and press Start listening again.
Is my playing sent anywhere?
No. There is no server in this tool at all. Audio frames are analysed in the page and discarded immediately; nothing is stored, recorded or transmitted. The only things saved are your chosen instrument and reference pitch, in this browser.
Related Tools
Updated August 23, 2026