Automata is a .NET library that provides algorithms for composing and analyzing regular expressions, automata, and transducers. In addition to classical word automata, it also includes algorithms for analysis of tree automata and tree transducers. The library covers algorithms over finite alphabets as well as their symbolic counterparts. In symbolic automata concrete characters have been replaced by character predicates. Such predicates can range over very large or even infinite alphabets, like integers. Predicates can be supported by an SMT solver as a plugin.