Regex Automaton Studio

Parse regular expressions, construct Thompson ε-NFAs, derive DFAs, edit transitions visually, simulate strings, and regenerate an equivalent regular expression with state elimination.

Thompson Construction ε-NFA & DFA State Elimination Import / Export

Regular Expression

Use | for union, implicit concatenation, * for Kleene star, + for one or more, ? for optional, and ε or \e for epsilon.
Supported syntax
aLiteral symbol abConcatenation a|bUnion a*Zero or more a+One or more a?Optional εEmpty string \*Escaped operator as a literal
Ready. Build an automaton from the expression above.

Simulation

Import, Export & Diagnostics

Automaton Visualisation

No automaton to display Enter a regular expression and select “Build ε-NFA”.
None 0 states 0 transitions Alphabet: ∅ Drag to pan · Wheel to zoom
State Initial Accepting Actions
Use ε or leave the symbol empty for epsilon.
From Symbol To Action
Step 0 of 0
No validation has been run.
No expression generated.
Equivalent regular expressions can look different while describing exactly the same language. State elimination may also produce a longer expression than the original.