What is a regular expression?

A regular expression (regex) is a pattern that matches text strings. It uses special characters to define patterns: . (any character), * (zero or more), + (one or more), ? (optional), [] (character set), ^ (start), $ (end). Regex is used for search, validation, and text processing.

How do I test a regex pattern?

Enter your regex pattern in the tester, add sample text, and see matches highlighted in real-time. The tester shows which parts of text match, capture groups, and helps debug pattern issues. Try different patterns to understand how they work.

What are common regex patterns?

Common patterns: email (/^[\w-\.]+@[\w-]+\.[a-z]{2,}$/), phone (/^\d{3}-\d{3}-\d{4}$/), URL (/^https?:\/\/.../), number (/^\d+$/), word (/^[a-zA-Z]+$/). Each pattern has variations depending on exact requirements.

Regex Tester - Test Regular Expressions

Regex Pattern

Test Text

What is Regex Tester?

Regular expressions (regex) are powerful pattern-matching tools used to search, validate, and manipulate text. A regex defines a search pattern using special characters and syntax that can match specific strings, ranges of characters, or complex text patterns. Regex is essential for data validation, text parsing, search functionality, and string manipulation in virtually every programming language.

How to Use

Enter your regex pattern in the pattern field (without surrounding slashes).
Toggle flags: g (global) finds all matches, i (case-insensitive), m (multiline).
Paste or type the text you want to test against in the test text area.
Click 'Test' to execute the regex and see all matches highlighted.
Review the matches list below to see each captured result.
Use 'Load Sample' to see an email-matching regex example.

Why Use This Tool?

Instant pattern testing with live visual highlighting of matches

Support for all standard regex flags (global, case-insensitive, multiline)

Clear error messages for invalid regex patterns

Match count and individual match display for easy analysis

Learn regex by experimenting with patterns and seeing results immediately

Debug complex patterns before using them in your code

Tips & Best Practices

Start simple - basic patterns like \d+ (digits) or \w+ (words) are easy to understand
Use anchors ^ and $ to match the start or end of a line/string
Escape special characters with backslash: \., \*, \?, etc.
Character classes like [a-z] or [0-9] define ranges to match
Quantifiers: * (zero or more), + (one or more), ? (zero or one), {n,m} (range)
Groups with parentheses () capture parts of matches for extraction

Frequently Asked Questions

What are the most common regex patterns?

Common patterns include: \d+ for numbers, \w+ for words/identifiers, [a-zA-Z]+ for letters only, \s+ for whitespace, \b for word boundaries, .+ for any characters, and \b\w+@\w+\.\w+\b for basic email matching. These patterns form the building blocks for more complex regex expressions.

What do the regex flags mean?

g (global) - finds all matches in the text, not just the first one. i (case-insensitive) - matches regardless of uppercase/lowercase differences. m (multiline) - makes ^ and $ match at line boundaries, not just string boundaries. These flags can be combined for powerful pattern matching.

Why is my regex not matching?

Common reasons include: missing escape characters for special symbols, incorrect anchors (^$ vs \b), wrong flag settings (case sensitivity), typos in the pattern, or the pattern being more restrictive than intended. Check each part of your pattern and test with simple examples first.

How do I match special characters literally?

Escape special regex characters with a backslash: \., \*, \+, \?, \|, $, $, \[, \], \{, \}, \^, \$, and \. For example, to match a literal dot in an email, use \w+\.\w+ not \w+.\w+.

Can I use this regex in my code?

Yes! The patterns tested here work in JavaScript, Python, Java, PHP, Go, and most programming languages. Minor syntax differences exist (like escaping backslashes in some languages), but the core regex syntax is standardized across platforms.

How do I capture parts of a match?

Use parentheses () to create capture groups. For example, (\d+)-(\d+)-(\d+) creates three groups that capture each part separately. In your code, these groups can be extracted individually for processing specific parts of matched text.

Regex Tester