S-folds are analogues of manifolds where transition functions are not just coordinate changes, as in any theory of gravity, but also involve elements of the S-duality group. Peculiar solutions like this have been the subject of intense speculation in the past few years, but it is usually hard to establish their existence, because the string coupling necessarily becomes strong in some region. I will present some classes of S-folds with an AdS4 spacetime. They have supersymmetric CFT duals, and their sphere partition function can be computed, showing agreement with the supergravity result when the fields are varying slowly. This gives nontrivial evidence of their existence.