Regex Tester
Test regular expressions with live match highlighting, capture group inspection, and find-and-replace. Uses your browser's JavaScript RegExp engine. Free. No sign-up.
How it works
- 1Enter your regex
Type a regular expression and toggle flags like global (g), case-insensitive (i), multiline (m), dotAll (s), or unicode (u).
- 2Add test text
Paste or type the text you want to match against. Matches are highlighted in real time as you type.
- 3Inspect results
View all matches with positions, inspect capture groups, or test find-and-replace with $1, $2, and $& references.
Why You Need a Regex Tester
Regular expressions are one of the most powerful text-processing tools in a developer's toolkit. They appear everywhere: form validation, log parsing, data extraction, search-and-replace in code editors, and route matching in web frameworks. Yet writing a regex from scratch and getting it right on the first try is notoriously difficult. A dedicated regex tester lets you iterate on your pattern in real time, see exactly what matches and what doesn't, and catch edge cases before they reach production.
Live match highlighting is the key feature that separates a good regex tester from a plain text editor. As you type your pattern, matches light up instantly in the test string. You can see at a glance whether your pattern is too greedy, too narrow, or matching unintended substrings. The color-coded highlighting for capture groups makes it easy to verify that your grouping parentheses are in the right place.
The capture groups panel shows you exactly what each group captured for every match. This is essential when building patterns for data extraction, such as pulling dates, emails, or structured identifiers out of unstructured text. Named capture groups make your patterns self-documenting and easier to maintain in complex codebases.
The replace mode lets you test find-and-replace operations using backreferences like $1, $2, and $&. This is invaluable for code refactoring, log transformation, and data cleanup tasks. You can see the replacement result in real time without risking changes to your actual files.
All processing happens entirely in your browser using the native JavaScript RegExp engine. Your patterns and test strings never leave your device, making this tool safe for sensitive data like API responses, log files, and configuration strings. There is no server, no logging, and no storage.