Changing the tuning is one of the quickest ways to find new sounds on a guitar you already know. Drop D gives you a deep bass note and one-finger power chords. Open tunings ring a full chord on the open strings and make slide guitar easy. DADGAD and the other modal tunings drone beautifully under a melody.
This tuner holds 42 guitar tunings, grouped as drop, open, modal, lowered and other. Search by name or by notes, pick one, and the page shows exactly which strings change and by how much: for example, the 6th string down a whole step and everything else the same. Then tune with the microphone, or by ear with the reference tone for each string.
Make your own. The builder lets you raise or lower each string a semitone at a time, hear each note, name the result and save it. Saved tunings appear in every tuner on the site, and the share link carries the exact notes so you can send it to a friend or a student.
Tuning strings up adds tension. When a tuning raises any string three semitones or more, the page warns you, so you can go slowly or fit a lighter string first.