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Regex Reversi

Each lesson gives you two lists: strings to match (green) and strings to avoid (red). Type a regex and the board lights up live. 15 lessons take you from literals to lookaheads.

0 / 15 solved
lesson 1 / 15· first steps

Just type the letters

teaches literal characters

Regex matches anywhere in a string by default. Type the literal text you want to find — the simplest possible pattern.

// your regex
length 0·par 3
//
should match0 / 4 ok
✗dog
✗doggo
✗lapdog
✗dogcatcher
should NOT match3 / 3 ok
✓cat
✓rat
✓bat
// quick reference
abcMatch the literal characters anywhere in the string
// lessons

Lessons unlock as you complete them. Click any unlocked lesson to revisit.