regexle (ithea)
Test strings and deduce the hidden regular expression
In this version of Regexle, the game hides a secret regular expression and you must work out what it is. You type test strings, and the game tells you whether each one matches. When you think you know the pattern, you enter your guess. If it is wrong, the game shows you a string that proves the difference.
Free · No login · Browser · New puzzle daily · Beginner
About regexle (ithea)
This is a good way to practise thinking about what a regex really accepts and rejects. A cheat sheet on the page explains the symbols, so beginners can play too.
It runs in the browser with no account, and you can create your own puzzle and share it as a link.
On Breakpoint since 23 Oct 2026.