In this article, we improve the partial regularity theory for minimizing 1/2-harmonic maps of [30,33] in the case where the target manifold is the (m − 1)-dimensional sphere. For m 3, we show that minimizing 1/2-harmonic maps are smooth in dimension 2, and have a singular set of codimension at least 3 in higher dimensions. For m = 2, we prove that, up to an orthogonal transformation, x/|x| is the unique non trivial 0-homogeneous minimizing 1/2-harmonic map from the plane into the circle S 1 . As a corollary, each point singularity of a minimizing 1/2-harmonic maps from a 2d domain into S 1 has a topological charge equal to ±1.