Open G tuning (D-G-D-G-B-D) tunes the guitar so that strumming all six open strings sounds a G major chord. Compared to standard tuning, the 6th, 5th, and 1st strings are each lowered one whole step (E→D, A→G, E→D), while the 4th, 3rd, and 2nd strings stay the same. Because every open string belongs to a G chord, you can play major chords by barring a single fret straight across.

Start in standard tuning (EADGBE). Lower the 6th string from E2 to D2, lower the 5th string from A2 to G2, and lower the 1st string from E4 to D4. Leave the 4th (D3), 3rd (G3), and 2nd (B3) strings exactly where they are. Use the tuner above — it is preset to Open G, so each string will show its Open G target as you play.

Open G is most famous as Keith Richards' tuning with the Rolling Stones — 'Start Me Up', 'Brown Sugar', 'Honky Tonk Women', and 'Can't You Hear Me Knocking' all use it (Richards typically removes the low 6th string for a 5-string Open G). It's also a cornerstone of Delta blues slide guitar, heard in Robert Johnson's 'Walking Blues' and countless Howlin' Wolf and Son House recordings.

Because all six open strings form a G major chord, a slide laid straight across any fret produces a full major chord. This lets slide players move complete chords up and down the neck with one smooth motion, instead of fretting individual notes. Open G (and Open D) are the two most common slide-guitar tunings in blues, rock, and country.

Three strings change. In standard tuning the 6th, 5th, and 1st strings are E2, A2, and E4; in Open G they drop to D2, G2, and D4. The middle three strings (D3, G3, B3) are identical to standard. This means open strings ring out a G chord, and barre-style major chords become a one-finger shape across a single fret.