Using the recent theory of noncommutative motives, we compute the additive invariants of orbifolds (equipped with a sheaf of Azumaya algebras) using solely "fixedpoint data". As a consequence, we recover, in a unified and conceptual way, the original results of Vistoli concerning algebraic K-theory, of Baranovsky concerning cyclic homology, of the second author and Polishchuk concerning Hochschild homology, and of Baranovsky and Petrov, and Cǎldǎraru and Arinkin (unpublished), concerning twisted Hochschild homology; in the case of topological Hochschild homology and periodic topological cyclic homology, the aforementioned computation is new in the literature. As an application, we verify Grothendieck's standard conjectures of type C C and D, as well as Voevodsky's smash-nilpotence conjecture, in the case of "low-dimensional" orbifolds. Finally, we establish a result of independent interest concerning nilpotency in the Grothendieck ring of an orbifold. 14A15, 14A20, 14A22, 19D55 1. Introduction 3004 2. Preliminaries 3014 3. Action of the representation ring 3021 4. Decomposition of the representation ring 3022 5. G 0-motives over an orbifold 3025 6. Proofs: decomposition of orbifolds 3034 7. Proofs: smooth quotients 3036 8. Proofs: equivariant Azumaya algebras 3038 9. Grothendieck and Voevodsky's conjectures for orbifolds 3041 Appendix: Nilpotency in the Grothendieck ring of an orbifold 3043 References 3045