How to read guitar chord diagrams

Chord diagrams (boxes) are read as if you are looking straight at the fretboard. The vertical lines are strings; the rightmost line is the thinnest string (high E), and the leftmost is the thickest (low E) unless the chart says otherwise.

Frets and the nut

The thick horizontal line at the top is the nut (fret zero). Horizontal lines below it are frets. A dot on a string between two lines means you press that string at that fret.

O, X, and numbers

An O above a string means play it open. An X means do not play that string (mute it or skip it). Small numbers sometimes show suggested left-hand fingers (1 index through 4 pinky).

Try it in the tool

Open the Chord builder and compare the on-screen neck to a printed chart: the colored dots match root, third, and fifth of the triad.