Online tuner

Play a note and this page names it, tells you its frequency, and shows how many cents sharp or flat you are. It is chromatic, so it works for any instrument that plays one note at a time, and it has the standard tunings for guitar, ukulele and violin built in.

The microphone only comes on when you press Start. The sound is analysed here in the page, by the script this page loads: nothing is recorded, nothing is uploaded, and there is no server involved at any point. Press Stop, close the tab or switch to another one and the microphone is released again. Refusing permission is a perfectly fine answer — nothing else on this page needs it. The only things kept between visits are your A4 setting and the tuning you picked, stored in this browser.

What it does, and where it gives up

It follows one note at a time, roughly from the A below the bass clef up to the A two octaves above the treble staff. Play a chord and the reading will wander, because a single frequency is the wrong answer to that question. A noisy room, a phone speaker playing in the background or a very soft note will all show up as a needle that refuses to settle.

It reads the microphone your browser gives it, with the browser's noise suppression and automatic gain switched off — both are tuned for speech and will quietly reshape a held note. A laptop's built-in microphone is usually good enough for tuning; it is not a measurement instrument.

If the needle never moves

The line under the dial says what the page is hearing. If it keeps saying no sound is arriving after you have allowed the microphone, the browser is usually handing the page a different input than you expect — a headset, a virtual device, or a muted one. Check which microphone this site is using in the browser's own settings for the page. Browsers differ in how they hand audio to a page, so if one refuses to cooperate, another may not.

A=440, and when it isn't

The reference is adjustable from 415 to 466 Hz. A=415 is the usual baroque pitch, several orchestras tune to 442 or 443, and an old piano may simply have settled somewhere of its own. Everything on the dial is measured against whatever you set here.

The tuner in the app

Scoreflection has its own tuner, and it costs nothing there either: a ±50-cent meter with instrument presets, custom tunings and reference tones, for instruments that are not tuned in the usual way. If your instrument does not sit at concert pitch at all, the app can calibrate against it — you play held notes from C2 to C6, and it compensates by up to fifty cents either way instead of marking you wrong.

The app also goes past what any tuner can do: it reads the score you are playing and marks every notehead as correct, wrong, missed or mistimed. Reading scores, playback, the metronome and the tuner are free and need no account. Being listened to and graded is the paid Practice plan, which needs you to be signed in.

Keeping time rather than pitch? There is an online metronome here too.