RegExp Equivalence Checker

How to use:

Enter two JavaScript regular expressions (without the surrounding slashes) and click "Check Equivalence". The tool will determine if both expressions match exactly the same set of strings. If they're not equivalent, it will show example strings that demonstrate the difference.

Examples:

• a* and a+ are not equivalent
• a|b and b|a are equivalent
• (ab)+ and ab(ab)* are equivalent

Supported syntax:

• Quantifiers: a*, a+, a{3,10}, a?
• Alternation: a|b
• Character classes: ., \w, [a-zA-Z], ...
• Escaping: \$, \., ...
• (Non-)capturing groups: (?...), (...)
• Positive/negative lookahead: (?=...), (?!...)

Unsupported syntax:

• RegExp flags: g, i, m, s, u, y
• Unicode property escapes: \p{...}, \P{...}
• Backreferences: \1, \2, ...
• Lookbehind assertions: (?<=...), (?<!...)
• Word boundary: \b, \B

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