Free Regex Tester Online: Test Regular Expressions with Live Highlighting

What Is Regex and Why Test It Online?

Regular expressions (regex) are patterns used to match, search, and manipulate text in programming. They're used for everything from email validation to log parsing to data extraction.

The problem: regex syntax is notoriously difficult to write correctly, especially for complex patterns. Debugging regex inside application code means compile-test-fix cycles that waste time. Our free regex tester at timarsouss.com/tools/regex-tester lets you test patterns in real-time with visual match highlighting — catching issues before they reach production.

How to Test Regex Online

1. Go to timarsouss.com/tools/regex-tester 2. Enter your pattern in the Pattern field (without surrounding slashes) 3. Enter flags in the Flags field (g for global, i for case-insensitive, m for multiline) 4. Paste your test string below 5. Matches highlight in real-time — no button needed

Essential Regex Flags Explained

	Flag	Meaning	Example Use

|---|---|---|

	g	Global — find all matches, not just first	Find all emails in a document
i	Case-insensitive	Match "Hello", "hello", "HELLO"
m	Multiline — ^ and $ match line start/end	Validate each line independently
s	Dotall — . matches newlines too	Match across line breaks
u	Unicode — handle emoji and Unicode	International text processing
i	Case-insensitive	Match "Hello", "hello", "HELLO"
m	Multiline — ^ and $ match line start/end	Validate each line independently
s	Dotall — . matches newlines too	Match across line breaks
u	Unicode — handle emoji and Unicode	International text processing

10 Useful Regex Patterns to Test

Email validation: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ URL matching: https?:\/\/(www\.)?[-a-zA-Z0-9@:%._+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b Phone number (US): ^\+?1?\s?\(?[0-9]{3}\)?[\s.-]?[0-9]{3}[\s.-]?[0-9]{4}$ IP address: ^(?:(?: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]?)$ Strong password: ^(?=.[a-z])(?=.[A-Z])(?=.\d)(?=.[@$!%?&])[A-Za-z\d@$!%?&]{8,}$ Date (YYYY-MM-DD): ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$ Credit card number: ^[0-9]{4}[- ]?[0-9]{4}[- ]?[0-9]{4}[- ]?[0-9]{4}$ Hex color code: ^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$ YouTube URL: ^(https?:\/\/)?(www\.)?(youtube\.com\/watch\?v=|youtu\.be\/)[A-Za-z0-9_-]{11}$ Whitespace cleanup: \s+ with replacement ' '

Test Your Regex Now

→ Free Regex Tester with Live Highlighting

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