Debuggex

Debuggex is an online visual regular expression tester that provides a graphical railroad-diagram visualization of regex patterns, helping developers understand exactly how their expressions work. It supports three major regular expression flavors: JavaScript, Python, and PCRE, covering the most common use cases across server-side and client-side development. The visual diagram renders the expression as a state machine flowchart, showing how the regex engine traverses through each character group, alternation, quantifier, lookahead, and capture group in sequence. This graphical representation makes it substantially easier to debug complex nested patterns compared to traditional text-only regex testers. Users can save and share regex patterns, add unit tests with expected match behavior, and browse a community library of pre-built expressions organized by category.