Guitar chord shapes in any key
Power, major, minor, dominant 7, minor 7 and major 7 shapes, with the notes each one actually sounds.
Every chord type here is shown as a real grip: the open shape where the root has one, and the movable barre shape otherwise. The distinction matters, because a movable shape is one thing you learn once and slide, whereas the open shapes each have to be learned individually.
Worth noticing as you flick between types: how little has to change. Major to minor is one finger. Major to dominant 7 is one finger. The shapes are far more closely related than their names suggest, and seeing that is quicker than memorising each as a separate picture.
A power chord is the odd one out — root and 5th only, no 3rd at all. That is exactly why it works under distortion, and why it sounds neither major nor minor.
Where they sit on the neck
The types divide into two groups by where they live. Open shapes only exist for the handful of roots with notes on open strings, and they are separate things to memorise: five for major (C, A, G, E and D), three for minor (Am, Em and Dm).
Movable shapes are one object each, slid along the neck, and their address is a string. An E-shape barre puts the root on the low E string. An A-shape barre puts it on the A string. A D-shape puts it on the D string. So finding any chord anywhere is a two-part question: which string do you want the root on, and where on that string is the root?
Worked through: A major with the root on the low E string is the 5th fret. G major with the root on the low E is the 3rd. C major with the root on the A string is the 3rd. Once the note names on those two strings are solid, every barre chord in every key is arithmetic you can do at speed.
How little changes between them
Flick between the types on one root and watch what actually moves. In open position in A, A major is x02220. Lower the B string by one fret and you have Am at x02210 — a single semitone, and that is the whole difference between major and minor.
Go back to A major and drop the G string from the 2nd fret to the open string: that is A7, x02020. Do the same to the Am and you have Am7, x02010. Fret that G string at the 1st instead of the 2nd and you have Amaj7, x02120.
Five chords, one root, and no shape more than one finger away from its neighbour. The names imply six unrelated objects with six unrelated moods. The grips say otherwise, and the grips are what you have to play.
Each type also has a job, which is worth knowing before you learn all six. Power chords carry riffs under gain. Dominant 7s are most of the vocabulary of a blues. Minor 7 is the usual grip for a minor groove, because a bare minor triad under a vamp often sounds thinner than the music wants. Major 7 belongs to softer material and will sound wrong in a blues, where the ♭7 is doing the work.
The common mistake
Learning the open shapes and stopping there. A player who only knows open chords can play comfortably in about half the keys and has to reach for a capo for the rest, which is fine until somebody counts in a tune in B♭. Barre shapes are harder for roughly a fortnight and then they are the only shapes you need, because each one covers all twelve roots by itself. If you are avoiding them, the problem is almost always thumb position rather than hand strength: the thumb belongs flat behind the neck, roughly opposite the second finger, not hooked over the top where it drags the wrist out of line.