Regex Tester

Regex Pattern Basics

Metacharacters define patterns:

• . - Any character
• \d - Digit
• \w - Word character
• \s - Whitespace
• ^$ - Start/end anchors

Quantifiers control repetition: * zero+, + one+, ? optional, {n,m} between n and m.

Common Regex Patterns

Pattern	Use
[\w.-]+@[\w.-]+\.\w+	Email
\d{3}[-.]?\d{3}[-.]?\d{4}	Phone
https?://[\w.-]+	URL
\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}	IPv4
#[0-9A-Fa-f]{6}	Hex color

Regex Flags

• g - Global, find all
• i - Case insensitive
• m - Multiline
• s - Dot matches newline

Advanced Patterns

(...) capture groups. ([a-z])\1 matches "aa". foo(?=bar) matches "foo" before "bar" (lookahead).

Frequently Asked Questions

How to test a regex?

Enter pattern, type test text, select flags, click "Test Match".

What are regex flags?

They modify pattern behavior: g (global), i (case insensitive), m (multiline), s (dotall).

Match special characters?

Escape with backslash: \. matches a literal period.

What are capture groups?

Parentheses () extract matched parts like (\d+) to capture digits.

Why no match?

Check escaping, verify flags (use g for multiple), ensure anchors are correct.

Case insensitive?

Enable the "i" flag checkbox.