Root on A string
x7898x
Edim is the E diminished chord. Its notes are E, G and B♭. A compact, tense triad. Every interval in this voicing is a chord tone.
x7898x
Numbers show frets from the low E string to the high e string; x means don't play that string.
Edim is the vii° chord in F major. That makes it a natural fit in songs written in those keys.
Every E, G and B♭ on the first 12 frets. The filled dots are the root, E. Build your own shape from any nearby group.
Other E chords
Other diminished chords