Regular Expression to Automaton Converter

Build an ε-NFA from a regular expression using Thompson's construction, step through the construction, convert the final ε-NFA to a DFA, and simulate input strings on both machines.

Regex with concat: -

Postfix: -

Current view: ε-NFA

Result: -

Enter a regex and click Build ε-NFA.

🧠 Regex Syntax Guide

a → single character
ab → concatenation
a|b → union
a* → zero or more a
(a|b) → grouping
a(b|c)*a → mixed expression

⚡ Click an Example

Start Accept Normal New/Highlighted step