This talk presents the notion of causal-consistent reversible debugging and its instance on Erlang provided by CauDEr. Reversible debugging allows us to explore an execution back and forth looking for the bug causing a visible misbehavior. Causal-consistent debugging tailors this approach to concurrent systems, where backward execution is not forced to undo the actions of a forward execution in reverse order, but can undo any action provided that its consequences, if any, are undone beforehand. CauDEr is a causal-consistent reversible debugger for the functional and concurrent language Erlang.