We study the index of \(\mathcal {N}=4\) Yang–Mills theory on \(S^3\times \mathbb {R}\) at large angular momenta. A generalized Cardy limit exhibits macroscopic entropy at large N. Our result is derived using free QFT analysis, and also a background field method on \(S^3\) . The index sets a lower bound on the entropy. It saturates the Bekenstein–Hawking entropy of known supersymmetric AdS \(_5\) black holes, thus accounting for their microstates. We further analyze the so-called MacDonald index, exploring small black holes and possibly new black holes reminiscent of hairy black holes. Finally, we study aspects of large supersymmetric AdS \(_7\) black holes, using background field method on \(S^5\) and ’t Hooft anomalies.