Regex to Automaton

See how regular expressions become finite automata. Watch Thompson's construction build an NFA, convert it to a DFA via subset construction, and step through matching character by character.

Regex to Automatonalpha

Regex Pattern

Test String

10 states, 10 transitions

Step 0/2

Match Progress

Start: ε-closure of q8 = {q8, q0, q4}

Active: {q8, q0, q4}

Step Log

Start: ε-closure of q8 = {q8, q0, q4}

Thompson's construction converts a regex into an NFA with ε-transitions. Subset construction then determinizes it into a DFA. All computation runs entirely in your browser.

Looking to test regex patterns with JavaScript's native engine? Try the Regex Tester.