Free Online Guitar Tuner
TunersBook is a free, accurate tuner for guitar, bass, ukulele and violin. Tap start, allow your mic, and tune right in the browser — standard and alternate tunings, with nothing recorded or uploaded.
Allow microphone access. Everything runs in your browser — nothing is recorded or uploaded.
How it works
Allow your mic
One tap. Audio is processed in your browser and never leaves your device.
Pluck a string
Let one string ring cleanly. The big note and the meter show what you're playing.
Tune to ±5 cents
Turn the peg until the needle centres and the string turns green. Done.
Alternate tunings
Pick any of these in the tuner above, or open a step-by-step guide.
Drop the low E a whole step to D for heavier riffs and easy power chords.
Every string down a semitone — warmer tone and easier on the voice (Hendrix, SRV).
Modal 'Celtic' tuning — lush, droney open chords loved in folk and fingerstyle.
Strum open for a G major chord — the classic slide and Keith Richards tuning.
Open D major — bright, ringing slide and fingerstyle tuning.
A tuner that's also your book of business.
We're building the professional toolkit the trade has never had on the web: every customer, every piano, every tuning — with inharmonicity fingerprints, automatic recall reminders and invoicing, on any device.
Get notified at launch →Frequently asked questions
Is the TunersBook guitar tuner free?
Yes — TunersBook is completely free with no sign-up and no app to install. It runs in any modern browser on your phone or computer.
Does the online tuner use my microphone?
Yes, with your permission. Your audio is processed locally in the browser and is never recorded or uploaded — nothing leaves your device.
How accurate is the tuner?
It detects pitch using time-domain autocorrelation and shows how many cents flat or sharp you are from the target. A string reads 'in tune' within ±5 cents. Autocorrelation stays accurate on low strings, where FFT-only tuners struggle.
Which instruments and tunings are supported?
Guitar (Standard, Drop D, Half Step Down, DADGAD, Open G, Open D), bass, ukulele and violin — 9 tunings across 4 instruments, with more on the way.
Is there a tuner for piano technicians?
A professional piano-technician toolkit — tuning records, recall reminders and invoicing — is in development. The free instrument tuner stays free.