We relate two different proposals to extend the étale topol-ogy into homotopy theory, namely via the notion of finite cover introduced by Mathew and via the notion of separable commutative algebra introduced by Balmer. We show that finite covers are precisely those separable commutative alge-bras with underlying dualizable module, which have a locally constant and finite degree function. We then use Galois the-ory to classify separable commutative algebras in numerous categories of interest. Examples include the category of mod-ules over a connective E∞-ring Rwhich is either connective or even periodic with π0(R)regular Noetherian in which 2acts invertibly, the stable module category of a finite group of p-rank one and the derived category of a qcqs scheme.