What is a regex tester?

A regex tester lets you write a regular expression and test it against sample text in real time. Matches are highlighted instantly and capture groups are displayed in a results table.

What regex flavour does this use?

This tool uses JavaScript's built-in RegExp engine, which supports standard syntax including lookahead, lookbehind, named groups, and Unicode escapes.

What are regex flags?

Flags modify how the regex engine matches: g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line breaks), and s (dotAll — . matches newlines).

Yes. Pattern matching runs in your browser using JavaScript's built-in RegExp engine.

Regex Tester

Write and test regular expressions with real-time match highlighting, capture group extraction, and common patterns.

Results

Enter a pattern and test string to see results

Regular Expression

Pattern

Flags

Common Patterns

Test String

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Everything you need to know

Real-Time Regex Testing

Type your regular expression and test string, and see matches highlighted instantly. No need to press a button — results update as you type. Each match is color-highlighted in the test string so you can visually confirm your pattern works.

Capture Groups & Match Details

The results table shows every match with its index position and any captured groups. This makes it easy to debug complex patterns with nested parentheses and understand exactly what each group captures.

Flag Support

Toggle regex flags with one click: g (global), i (case-insensitive), m (multiline), and s (dotAll). The tool shows your complete regex in /pattern/flags notation for easy copying.

Common Pattern Library

Don't remember the regex for emails, URLs, or IP addresses? Click a preset to load it instantly. The library includes patterns for emails, URLs, IPv4 addresses, US phone numbers, hex colors, ISO dates, HTML tags, and integers.

Client-Side Processing

Your regex and test data are processed in your browser. This makes it suitable for testing patterns against sensitive strings.

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