Jurriaan Rot Kleene Algebras and Bisimulation-up-to The axioms of Kleene Algebra (KA) are complete for language equivalence of regular expressions, and consequently one can prove KA identities by showing that certain regular expressions represent the same language. Language equivalence of regular expressions can be shown coinductively by establishing bisimilarity of associated deterministic automata. Bisimulation-up-to is a family of enhancements of the bisimulation proof method for processes, which has recently been generalized to the theory of coalgebras. We apply bisimulation-up-to to regular expressions, and derive a simplified proof technique for equations in KA.