Free Online Regex Tester
Test and debug regular expressions with live match highlighting, group extraction, and a common patterns library. Free, 100% client-side regex tester.
100% Client-Side · Your data never leaves your browserHow to Use Regex Tester
Enter your regular expression in the pattern field (without the surrounding slashes). Toggle flags using the buttons on the right of the input.
- Paste the text you want to search in the Test String area.
- Click Test or press Ctrl/Cmd+Enter. Matches are highlighted in the output and listed in the Match Details table below.
- Open Common patterns library to load a predefined regex — great for validation use cases like email, URL, or UUID.
- Use Copy regex to copy the complete expression including flags (
/pattern/flags).
Named capturing groups ((?<name>pattern)) appear as named columns in the Match Details table.
Frequently Asked Questions
What regex flavour does this tool use?
This tester uses JavaScript's built-in RegExp engine, which follows the ECMAScript specification. It supports most Perl-compatible syntax but does not support lookbehind assertions in all older browsers.
What do the flag toggles do?
g (global) finds all matches instead of stopping at the first. i makes matching case-insensitive. m makes ^ and $ match line boundaries. s makes . match newlines. u enables full Unicode mode including surrogate pair handling.
How many matches does the tool show?
The highlighted output shows all matches in the test string. The Match Details table displays up to the first 100 individual matches with their index positions and captured groups.
How do I use capturing groups?
Wrap part of the pattern in parentheses, e.g. (\d{4})-(\d{2})-(\d{2}). Each captured group appears in the Groups column of the Match Details table. Named groups use the syntax (?<name>pattern).
Is the test string sent to any server?
No. All matching is done in your browser using the JavaScript RegExp API. No text or patterns leave your device.
What are the common patterns in the library?
The library includes patterns for email addresses, URLs, IPv4 addresses, phone numbers, hex colours, dates (YYYY-MM-DD), postal codes, credit card numbers, slugs, UUIDs, and more.