A strobe tuner for guitar, bass, violin and ukulele. Bass is read from its harmonics, so even a low B tunes steadily on a phone. It is free and runs in your browser on a phone, tablet or computer, even offline.
Your browser will ask for the microphone. Sound is analysed on this device and never sent anywhere. Hold the phone close to the instrument, or to the amp, in a quiet room.
E2
--¢
target 82.41 Hz
play a string
-50-250+25+50
Reference pitch
440 Hz is the standard. Change it to match a piano, a recording or a group that tunes a little higher or lower.
Questions
Is String Tuner free?
Yes, it is free to use. There is no account and nothing to sign up for.
Which instruments can it tune?
Guitar, bass (4, 5 and 6 string), violin and ukulele, with common alternate tunings such as drop D, DADGAD, open G and low G ukulele. Chromatic mode tunes any note on any instrument.
Why does it work better for bass than most tuners?
Phone and laptop microphones hardly pick up the fundamental of a low bass string. String Tuner reads up to eight harmonics instead, corrects for the stiffness of the string, and skips the sharp attack of the pluck, so the reading on a low E or B is steady.
Does it send my audio anywhere?
No. Sound is analysed on this device and never sent anywhere. Settings are saved in this browser.
Does it work without an internet connection?
Yes. After the first visit it is stored on the device and opens with no connection. It can also be installed as an app.
How it works
A plucked or bowed string vibrates at its fundamental and at a series of harmonics above it. Most tuners measure only the fundamental. String Tuner measures several harmonics at once (up to eight on a low bass string) and works out the pitch from all of them, which gives a steadier reading, above all where the fundamental is weak.
Strings are a little stiff, so their upper harmonics sit slightly higher than exact multiples of the fundamental. On a thick bass string the difference adds up to several cents by the eighth harmonic. The tuner measures this stiffness as you play and corrects for it, so the harmonics give the right answer instead of a sharp one.
Why bass is different
The low E of a bass is 41 Hz and the low B of a five-string is 31 Hz. Phone and laptop microphones barely hear frequencies that low, so a tuner that waits for the fundamental gets a weak, jumpy signal. The harmonics of the same string sit where microphones work well. String Tuner also waits for the first moment of each pluck to pass, because a string plucked hard rings a little sharp before it settles.
The screen
Note name: the string or note it is listening for. Below it, the target frequency and how many harmonics are being read.
Cents: how far off the string is. A cent is a hundredth of a semitone. Plus means sharp (too high), minus means flat. A ~ in front means the string is far off and the reading is rough.
Strobe: the stripes drift right when sharp, left when flat, and stand still when the string is on target. It shows smaller errors than the cents readout. Tune until the stripes are nearly still.
Needle: a coarse view, plus or minus 50 cents. The green band is plus or minus 2.
Level bar: shows the microphone is hearing you. If it barely moves, get the phone closer or play harder.
Strings: one button per string, with a mark showing its last reading: green within 2 cents, amber within 5, red further out.
Controls
Instrument and Tuning: pick the instrument and the tuning you want. The tuner remembers the tuning for each instrument.
Auto: follows whichever string you play. Best for a quick check.
Tapping a string: locks onto it. Use this when a string is far off, or Auto may decide you are playing the neighbouring string. In Chromatic mode the arrows step through the notes.
Play target: plays the target pitch, with harmonics so that low notes can be heard from a phone speaker.
Pitch of A4: 440 Hz is the standard. Every target follows it.
Instruments and tunings
Guitar: standard (E A D G B E), drop D, half step down, DADGAD, open G and open D.
Bass: 4-string (E A D G), 5-string (B E A D G), 6-string (B E A D G C), drop D and half step down.
Violin: G D A E.
Ukulele: standard with a high G (G C E A), low G, and baritone (D G B E).
Chromatic: any note, for anything else (viola, cello, mandolin, banjo, a harp string, your voice).
Tips for good readings
Work in a quiet room, one string at a time, and mute the strings you are not tuning.
Tune up to the note. If a string is sharp, bring it below the target first, then come up to it. The string holds its pitch better.
Bass: pluck firmly with a finger rather than slapping, and let the note ring. Hold the phone near the body of an acoustic bass, or near the amp's speaker.
Guitar: pluck over the soundhole or the neck pickup. Harmonics and very hard picking can confuse any tuner.
Violin: pluck or bow the open string. Use the fine tuners for the last few cents, and the pegs only when a string is well off.
Ukulele: new nylon strings stretch for days. Expect to retune often at first.
Internet connection and your data
Everything runs on your device, so the tuner needs no internet connection. After your first visit the app is stored on the device and opens even with no signal at all.
Your instrument, tunings and readings are saved in this browser. Nothing is uploaded, and the microphone audio never leaves your device.
Install it as an app
Installed, the tuner gets its own icon and window and opens without a connection.
Chrome or Edge (computer or Android): tap Install app at the bottom of the page, or choose Install from the browser menu.
iPhone and iPad (Safari): tap Share, then Add to Home Screen.