What is an online regex tester?

An online regex tester lets you write a regular expression and test it against a sample string in real time, highlighting every match and showing captured groups — without writing any code.

What regex flags does this tool support?

This tool supports the four most common JavaScript regex flags: g (global — find all matches), i (case insensitive), m (multiline — ^ and $ match line boundaries), and s (dotall — dot matches newlines).

What regex syntax does this tool use?

This tester uses the JavaScript RegExp engine. The syntax is compatible with most modern languages for common patterns, including Python re, Java, Go, and PHP PCRE.

Regex Tester Online

Write a regular expression, paste a test string, and instantly see every match highlighted. Supports JavaScript regex with all standard flags.

Samples:

Regular Expression

/ /g

Enter a pattern above

Test String

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How to Use the Online Regex Tester

Type your regular expression in the pattern field, choose your flags, then paste the string you want to test. Matches are highlighted in real time — the first match in blue and subsequent matches in yellow.

What Are Regex Flags?

g — Global: find all matches, not just the first one
i — Case insensitive: hello matches Hello, HELLO, etc.
m — Multiline: ^ and $ match start/end of each line
s — Dotall: . matches newline characters too

Common Regex Patterns

Email address: [\w.+-]+@[\w-]+\.[a-zA-Z]{2,}
URL: https?://[^\s]+
Phone number: \+?[\d\s\-().]{7,}
IP address: \b\d{1,3}(\.\d{1,3}){3}\b
Date (YYYY-MM-DD): \d{4}-\d{2}-\d{2}
Hex color: #[0-9a-fA-F]{3,6}\b

About This Tool

This regex tester runs entirely in your browser using JavaScript's native RegExp engine. No data is sent to any server. The JavaScript regex syntax is compatible with most modern programming languages including Python (re module), Java, and Go for common patterns.

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