Regex Tester

Test and debug regular expressions with real-time matching, syntax highlighting, and capture group analysis.

What is the Regex Tester?

Our Free Online Regex Tester is a powerful tool designed for developers, data analysts, and anyone working with text patterns. Regular expressions (regex) are essential for pattern matching, data validation, and text processing, but they can be tricky to get right. This tool provides instant visual feedback to help you write and debug regex patterns efficiently.

The regex tester runs entirely in your browser, ensuring your sensitive data never leaves your device. Whether you're validating email addresses, parsing log files, extracting data from text, or building complex search patterns, our tool makes regex development fast and intuitive.

With features like real-time match highlighting, capture group display, and a library of common patterns, you can quickly test and refine your regular expressions. The tool supports all standard regex flags including global, case-insensitive, multiline, and unicode matching.

Quick Regex Patterns

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Basic email validation

URL

https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)

HTTP/HTTPS URLs

Phone (US)

$?([0-9]{3})$?[-. ]?([0-9]{3})[-. ]?([0-9]{4})

US phone numbers

Date (YYYY-MM-DD)

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

ISO date format

IPv4

\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b

IP addresses

Hex Color

#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})

Hex color codes

Regex Cheat Sheet

Character Classes

\d - Digit
\w - Word character
\s - Whitespace
. - Any character

Quantifiers

* - 0 or more
+ - 1 or more
? - 0 or 1
{n,m} - Between n and m

Anchors

^ - Start of string
$ - End of string
\b - Word boundary

How to Use the Regex Tester

Enter Your Pattern: Type your regular expression pattern in the pattern field. You can write it from scratch or click one of the common patterns to load a pre-built example.
Select Flags: Choose appropriate flags for your pattern. Enable the "g" (global) flag to find all matches, "i" for case-insensitive matching, "m" for multiline mode, or any combination that suits your needs.
Add Test String: Input the text you want to test your pattern against. This can be a single line or multiple lines of text.
Test Pattern: Click the "Test Pattern" button to execute the regex against your test string. The tool will instantly show all matches with highlighting.
Review Results: Examine the highlighted matches in your test string. The tool displays match count, positions, and capture groups if your pattern includes them.
Refine and Iterate: Adjust your pattern based on the results and test again. The instant feedback loop helps you quickly perfect your regex.

📊

Common Use Cases & Examples

Email Validation

Pattern: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

This pattern validates email addresses, ensuring they have the proper format with a local part, @ symbol, domain, and top-level domain.

URL Extraction

Pattern: https?://[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}(/.*)?

Use this to find HTTP or HTTPS URLs in text. The pattern matches the protocol, domain, and optional path.

Phone Number Formatting

Pattern: ^(\+1)?[-.\s]?$?\d{3}$?[-.\s]?\d{3}[-.\s]?\d{4}$

This validates US phone numbers in various formats: (123) 456-7890, 123-456-7890, 123.456.7890, or with +1 country code.

Date Extraction

Pattern: ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$

Match dates in YYYY-MM-DD format, ensuring valid month and day ranges.

Frequently Asked Questions

What is a regular expression (regex)?

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

What are regex flags and what do they mean?

Regex flags modify the behavior of the pattern: g (global) finds all matches, i (case insensitive) ignores case, m (multiline) treats ^ and $ as line boundaries, s (dotall) makes . match newlines, u (unicode) enables full unicode support, and y (sticky) matches only from lastIndex.

How do I test my regex pattern?

Enter your regular expression pattern in the pattern field, select appropriate flags, input your test string, and click "Test Pattern". The tool will highlight all matches and show capture groups if your pattern includes them.

What are capture groups in regex?

Capture groups are portions of a regex pattern enclosed in parentheses (). They allow you to extract specific parts of matched text. For example, (\d{3})-(\d{4}) would capture area code and number separately from a phone number.

Is my data safe when using this regex tester?

Yes, absolutely! All regex testing happens entirely in your browser. Your patterns and test strings never leave your device or get sent to any server, ensuring complete privacy and security.

Pro Tips for Regex Success

Start simple Begin with basic patterns and gradually add complexity. Test each addition to ensure it works as expected.
Use capture groups wisely Parentheses create capture groups that extract matched portions. Use non-capturing groups (?:...) when you don't need extraction.
Escape special characters Characters like ., *, +, ?, etc. have special meanings. Use backslash (\) to match them literally.
Test with edge cases Try your pattern with unusual inputs, empty strings, and boundary conditions to ensure robustness.

📊

Pro Regex Tips