Kepma Online Tuner · Professional Chromatic and Instrument Tuner with Spectrum Analysis
The Kepma online tuner runs entirely in your browser: open the page, allow microphone access and the needle settles within a second. Nothing is uploaded and no connection is required once the page has loaded. It is built for guitar work but equally at home with bass, ukulele, violin, erhu, guqin or any fretted or fretted-less instrument, because the reference database covers more than a hundred tunings across nine instrument families.
What it does beyond showing you a note
The detector uses the McLeod Pitch Method, which measures the time-domain signal rather than just picking the loudest FFT bin. That distinction matters: on many instruments the second harmonic is stronger than the fundamental, so a naive tuner reports the wrong note an octave up. A median filter suppresses octave jumps, and a 22 Hz high-pass plus a 2.2 kHz low-pass at the input reject rumble and hiss before anything is measured. Accuracy sits around ±0.1 cents.
Temperaments, transposition and the reference pitch
Seven historical temperaments are included, from equal temperament through just intonation, Pythagorean, quarter-comma meantone, Werckmeister III, Kirnberger III and Vallotti, each with a plain-language description of where it came from and what it costs you. Transposing instruments are handled by listing them in B-flat, E-flat, F, A, G and D. The reference pitch is adjustable from 380 to 520 Hz, with one-tap presets for the common historical values from 415 Hz Baroque through 440 Hz international standard to 445 Hz Viennese.
Cents, the spectrum view and octave stretch
The cents needle gives ±50 cents of resolution with a clearly marked ±5-cent in-tune zone, and the spectrum view shows the fundamental alongside its harmonics so you can see why a note reads where it does. The octave stretch control reproduces the Railsback curve that piano tuners use to align harmonics across octaves. Hold a string and the reference tone together to hear the beating slow down as you close in; when the beat disappears you are there.
Custom tunings and everyday use
Any tuning can be saved as a custom preset, named, edited and starred, and the whole set of settings plus your custom tunings can be exported to a file and re-imported on another device. Everything stays in local storage on your own machine. For field setup, running a luthier bench check or simply checking a new set of strings, it is the same three seconds every time.
