About Us
Last updated: 18 August 2026
Free Online Tuner is a free chromatic tuner that runs directly in your browser. There is no app to install, no account to create, and no paid version hiding behind the one you are using. It is published on two domains, one in English (freeonlinetuner.com) and one in Spanish (afinadoronline.es), but it is the same tool.
Who is behind it
The project is maintained by an independent developer, not a company or a team. It started from a very specific frustration: wanting to tune a guitar without downloading yet another app full of permission requests, full-screen ads and features nobody asked for. The goal was to do one thing, tuning, and do it well. If you have a question, a suggestion, or you have found a bug, you can write to us from the contact page; a real person reads those messages.
How the tuner works
When you press start, your browser asks for permission to use the microphone. From there the tuner captures the sound and analyses it in real time with the Web Audio API, the audio technology built into every modern browser.
Working out which note you are playing means finding the fundamental frequency of the signal, which is less trivial than it sounds: a guitar string does not produce a pure tone but a fundamental surrounded by harmonics that can easily fool a naive algorithm. We use YIN, an autocorrelation method designed precisely to avoid the most common octave errors. The result is compared against the theoretical frequency of the target string, and the difference is expressed in cents, one hundredth of a semitone. We treat a string as in tune when the deviation is under five cents, a margin below what the human ear comfortably distinguishes.
All of that analysis happens on your device. Audio is never recorded, never stored and never sent to any server, ours or anyone else's. The privacy policy explains this in detail.
Instruments and tunings
The tuner ships with guitar, bass and ukulele, covering their standard tunings as well as the most widely used alternatives: Drop D, half a step down, open tunings and so on. Every tuning lists the exact frequency of each string, so it also works as a reference if you prefer to tune by ear. We keep adding instruments and tunings as people ask for them.
Why there are ads
Running the site costs money, and the alternative to advertising would be charging for access or asking for a sign-up in order to monetise visitors' data. We would rather keep it free and usable without giving anything in return, so it is funded through Google AdSense. We try to keep the ads out of the way while you are actually tuning. You can see which cookies that involves, and how to turn off personalisation, in the privacy and cookie policy.
Technical requirements
It works in any modern desktop or mobile browser (Chrome, Firefox, Safari, Edge). Because microphone access requires a secure connection, the site only works over HTTPS. If your browser never asks for microphone permission, the most likely cause is that permission is already blocked for the site in your browser settings.