Surface heterogeneity is generally acknowledged as the major cause of liquid–solid friction, affecting whether droplets slide off the surface or stick to it. Now, a model surface of self-assembled monolayers has been used to investigate how molecular-scale surface heterogeneity affects water contact angle hysteresis and contact line friction. The high-coverage hydrophobic surface is slippery, as—counter-intuitively—is the low-coverage hydrophilic surface.