Bdim is a diminished, spelled B, D and F. In Ukulele (low G) tuning (G3 C4 E4 A4) the easiest shape is x212, which sits at fret 1, spans 1 fret and mutes 1 string. 12 positions for it are shown below, from the nut up to fret 13.
Notes and intervals
Note
B
D
F
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.
x212sits at fret 1, spans 1 fret and mutes 1 string4575sits at fret 4 and spans 3 frets7575sits at fret 5 and needs a barre across 3 strings at fret 5x11108sits at fret 8, spans 3 frets and mutes 1 string101110xsits at fret 10, needs a barre across 3 strings at fret 10 and mutes 1 stringx141314sits at fret 13, spans 1 fret and mutes 1 string711108sits at fret 7 and spans 4 frets4212sits at fret 1 and spans 3 frets421xsits at fret 1, spans 3 frets and mutes 1 string4215sits at fret 1 and spans 4 frets4515sits at fret 1 and spans 4 frets757xsits at fret 5, spans 2 frets and mutes 1 string
Keys Bdim belongs to
Bdim is diatonic to 8 of the 96 keys this app knows, playing a different role in each.