Gdim is a diminished, spelled G, Bb and Db. In Standard tuning (E2 A2 D3 G3 B3 E4) the easiest shape is 3453xx, which sits at fret 3, needs a barre across 4 strings at fret 3 and mutes 2 strings. 12 positions for it are shown below, from the nut up to fret 14.
Notes and intervals
Note
G
Bb
Db
Interval
1P
3m
5d
12 ways to play it
Ordered by how hard they are to fret, easiest first, one per position on the neck. Fret numbers are relative to the position marked beside each grid.
3453xxsits at fret 3, needs a barre across 4 strings at fret 3 and mutes 2 stringsxxx323sits at fret 2, spans 1 fret and mutes 3 stringsx1011011xsits at fret 10, spans 1 fret, lets 1 string ring open and mutes 2 stringsx10110119sits at fret 9, spans 2 frets, lets 1 string ring open and mutes 1 stringx108089sits at fret 8, spans 2 frets, lets 1 string ring open and mutes 1 string6450xxsits at fret 4, spans 2 frets, lets 1 string ring open and mutes 2 strings31502xsits at fret 1, spans 4 frets, lets 1 string ring open and mutes 1 stringxx5686sits at fret 5, spans 3 frets and mutes 2 stringsxxx086sits at fret 6, spans 2 frets, lets 1 string ring open and mutes 3 stringsxx11011xsits at fret 11, needs no stretch at all, lets 1 string ring open and mutes 3 stringsxxx151415sits at fret 14, spans 1 fret and mutes 3 stringsxx5323sits at fret 2, spans 3 frets and mutes 2 strings
Keys Gdim belongs to
Gdim is diatonic to 8 of the 96 keys this app knows, playing a different role in each.