Given a connected Riemannian manifold , an -dimensional Riemannian manifold which is either compact or the Euclidean space, ∈ [1, +∞) and ∈ (0, 1], we establish, for the problems of surjectivity of the trace, of weak-bounded approximation, of lifting and of superposition, that qualitative properties satisfied by every map in a nonlinear Sobolev space , (, ) imply corresponding uniform quantitative bounds. This result is a nonlinear counterpart of the classical Banach-Steinhaus uniform boundedness principle in linear Banach spaces.The space, the energy and the topology on this space are independent of the embedding and can be defined intrinsically [30].1.1. Extension of traces. We first consider relationships between a qualitative and quantitative properties for the problem of surjectivity of the trace. In the setting of linear Sobolev spaces, given ∈ (0, 1), ∈ (1, +∞) and a manifold which is either compact or the Euclidean space, the classical trace theory states that the restriction of continuous functions in ( × [0, +∞), ℝ) has a linear continuous extension to the trace operator tr ∶ +1∕ , ( × (0, +∞), ℝ) → , (, ℝ) and that the latter trace operator is surjective [1, Theorem 7.39;32, Chapter 10;61, Theorem 2.7.2]. A. Monteil is a postdoctoral researcher (chargé de recherches) by the Fonds de la Recherche Scientifique-FNRS; J. Van Schaftingen was supported by the Mandat d'Impulsion Scientifique F.4523.17, "Topological singularities of Sobolev maps" of the Fonds de la Recherche Scientifique-FNRS.