Regex Tester
Test regular expressions with real-time match highlighting, capture groups, and common pattern presets.
Enter a pattern and test string to see matches.
No matches found.
Enter a test string.
Enter a pattern.
About this tool
Test and debug regular expressions with real-time match highlighting, capture groups, and common pattern presets. Includes a regex cheat sheet. Free, browser-based.
Frequently asked questions
What is a regex tester?
A regex tester lets you write a regular expression and test it against text in real time, showing matches, capture groups, and positions as you type.
What regex flags are supported?
g (global), i (case-insensitive), m (multiline), s (dotAll), and u (unicode).
Will complex patterns freeze my browser?
No. Regex execution runs in a Web Worker with a 2-second timeout, so catastrophic backtracking patterns are killed gracefully.