Regex → Thompson NFA, step by step

Type a pattern and a string, then press Step (or the → key) to watch the set of active states move one character at a time.

Supported: literals, ., [a-z], [^…], |, *, +, ?, ( ), and \ before a metacharacter. Anything else is rejected, not guessed. Dashed edges are ε (free) moves. Yellow means active. Orange edges are the ones the last character used. Keys: ← → step, Space play, Home reset (when focus is not in a text box).