In the paper we show that every 6–3 Stewart–Gough (SG) platform has self-motions. This yields an example of self-motions for a class of SG platforms which are not architecturally singular. We present three types of self-motions, general self-motion if the platform is in some sense congruent to the base, a butterfly type self motion and a spherical four-bar mechanism selfmotion. For the last two cases there is no restriction for the geometry of the platform. We believe that this yields all possible self motions of the 6–3 platform, but we are not able to give the proof, corresponding equations are too complex.