How does the regex tester work?

Enter your regular expression pattern and test text. The tool will highlight matches in real-time, show capture groups, and provide detailed match information including positions and captured text.

What regex flags are supported?

We support common regex flags: Global (g), Case-insensitive (i), Multiline (m), Dot matches newline (s), Unicode (u), and Sticky (y). These can be combined for complex pattern matching.

How do capture groups work?

Capture groups are portions of the regex pattern enclosed in parentheses. They allow you to extract specific parts of the matched text. Named groups use the syntax (? pattern) for better readability.

Can I test complex regex patterns?

Yes, our regex tester supports all standard JavaScript regex features including lookaheads, lookbehinds, backreferences, character classes, quantifiers, and anchors.

Regex Tester

Professional regular expression testing tool. Test patterns, validate matches, capture groups, and analyze regex performance with real-time feedback.

Regular Expression Pattern

Global (g)

Case-insensitive (i)

Multiline (m)

Dot matches newline (s)

Unicode (u)

Test Text

Match Results

Enter a regex pattern and test text to see matches here.

Common Patterns

Whole Words

\b\w+\b

Digits

\d+

Letters

[a-zA-Z]+

\w+@\w+\.\w+

URLs

https?://[^\s]+

Phone Numbers

\d{3}-\d{3}-\d{4}

Hex Colors

#?[0-9a-fA-F]{6}

Dates

\d{4}-\d{2}-\d{2}

Regex Quick Reference

Anchors:

^ (start), $ (end), \b (word boundary)

Quantifiers:

* (0+), + (1+), ? (0-1), {n} (exactly n)

Character Classes:

\d (digit), \w (word), \s (space), . (any)

Groups:

( ) (capture), (?: ) (non-capture)

How Regex Tester Works

1. Enter Pattern

Input your regular expression pattern and select the appropriate flags for your matching requirements.

2. Add Test Text

Paste or type the text you want to test your regex pattern against. The tool supports multiline text.

3. View Results

See highlighted matches, capture groups, and detailed information about each match found in your text.

Frequently Asked Questions

What is a regular expression?

A regular expression (regex) is a sequence of characters that defines a search pattern. It's used for pattern matching within strings, commonly for validation, parsing, and text manipulation.

What regex engine does this tool use?

This tool uses JavaScript's built-in RegExp engine, which supports most standard regex features including lookaheads, backreferences, and Unicode matching.

How do I use capture groups?

Capture groups are created by enclosing parts of your regex in parentheses. They allow you to extract specific portions of matched text and reference them later.

Why isn't my regex working?

Common issues include incorrect escaping of special characters, wrong flag usage, or syntax errors. Check your pattern against the quick reference guide and test with simple examples first.