Regex Tester — Free Online Tool
Test and debug regular expressions online with live match highlighting. Supports JavaScript regex syntax with global, case-insensitive, and multiline flags.
About Regex Tester
Regular expressions (regex) are powerful text pattern matching tools used in programming, data validation, search-and-replace operations, and log analysis. Our regex tester provides a real-time environment for writing and debugging regular expressions. Enter your pattern and test string to see all matches highlighted immediately. Shows match count, group captures, match positions, and details about each match. Supports all JavaScript regex flags: global (g), case-insensitive (i), multiline (m), dotAll (s), and sticky (y). Includes a regex syntax quick-reference cheat sheet.
Frequently Asked Questions
What regex syntax does the tester use?
JavaScript regex syntax (ECMA-262). Compatible with most modern programming languages.
Does it show capture groups?
Yes — all capturing groups are shown with their matched content.
What flags are supported?
Global (g), case-insensitive (i), multiline (m), dotAll (s), unicode (u), and sticky (y) flags.
Can I do find-and-replace with regex?
Yes — enter a replacement pattern and see the substitution result.
Is there a regex cheat sheet included?
Yes — a quick reference for common regex syntax is shown below the tester.