What is a regular expression (regex) and why use it?

A regular expression (regex) is a sequence of characters that defines a search pattern. It's used for pattern matching in strings, data validation (like email or phone formats), text search and replace, and parsing complex text. Regex is supported in most programming languages and is essential for text processing tasks.

Is my regex pattern and test data safe?

Yes, absolutely! All regex testing happens entirely in your browser using JavaScript. Your patterns and test strings never leave your computer or get sent to any server. This ensures complete privacy and security for sensitive data or proprietary regex patterns.

What regex flags are supported?

Our regex tester supports all JavaScript regex flags: g (global - find all matches), i (case-insensitive), m (multiline - ^ and $ match line boundaries), s (dotAll - . matches newlines), u (unicode), and y (sticky - matches from lastIndex). You can combine multiple flags for complex patterns.

How do I test if my regex matches correctly?

Enter your regex pattern in the pattern field, add any flags you need, then type or paste your test string. The tool will highlight all matches in real-time and show you detailed match information including captured groups, match positions, and the total number of matches found.

Can I test regex for different programming languages?

This tool uses JavaScript regex syntax, which is very similar to regex in most languages (Python, Java, C#, PHP, etc.). However, some advanced features may differ between languages. The core patterns (character classes, quantifiers, anchors) work the same across all languages.

Does this work offline?

Yes! Once you've loaded the page, the regex tester works completely offline. You can bookmark this page and use it anytime without an internet connection, making it perfect for development on the go or in restricted environments.

Text Tools

Regex Tester

Test and debug regular expressions with real-time pattern matching, flags support, and detailed match results.

Pattern & Flags

Regular Expression

Flags

Global (g) - Find all matches

Case insensitive (i)

Multiline (m)

Dot all (s)

Common Patterns

Test String

Results2 matches

Highlighted Matches

Match Details

Match 1Position 14-33

Full match:support@example.com

Match 2Position 37-54

Full match:sales@company.org

Regex Flags

Use flags to modify how the pattern matching works: global (g), case-insensitive (i), multiline (m), and dot-all (s).

Real-time Testing

See matches highlighted in real-time as you type. View detailed information about each match and capture groups.

Privacy

All regex testing happens in your browser. Your patterns and test strings are never sent to any server.

How to Use Regex Tester

Test and debug regular expressions in three simple steps

Enter Your Regex Pattern

Type your regular expression pattern in the pattern field. Use standard regex syntax like \d for digits, \w for word characters, [a-z] for character ranges, etc.

Add Flags and Test String

Select any flags you need (g for global, i for case-insensitive, etc.) and enter or paste your test string. The tool will automatically test your pattern against the string.

Review Matches

See all matches highlighted in real-time with detailed information about each match, including captured groups and positions. Adjust your pattern as needed until it matches correctly.

Common Use Cases

Email Validation

Test regex patterns for validating email addresses, ensuring they match the correct format before form submission.

Data Extraction

Extract specific data patterns from text like phone numbers, dates, URLs, or custom formats using capture groups.

Input Validation

Validate user input formats like passwords, usernames, credit cards, or postal codes before processing.

Text Search

Search for complex patterns in logs, code, or documents using advanced regex features like lookaheads and backreferences.

Code Parsing

Parse and extract information from code, configuration files, or structured text using regex patterns.

Text Replacement

Test find-and-replace patterns before applying them to large files or codebases to ensure accuracy.