Regex Tester — Test Regular Expressions Online Free

How to use

1. Enter Pattern — Type your regular expression pattern (without delimiters)
2. Set Flags — Toggle flags like global (g), case-insensitive (i), multiline (m)
3. Test — Enter test text and see matches highlighted in real time

What Is a Regex Tester?

A regex tester lets you write a regular expression pattern, apply it to test text, and immediately see which parts of the text match. This real-time feedback loop makes it dramatically easier to develop and debug regular expressions compared to testing them in code.

Regular expressions (regex) are patterns used to match character combinations in strings. They're supported in virtually every programming language and are essential for text processing, validation, search, and data extraction.

How to Use Regular Expressions

Regular expressions use a concise syntax to describe text patterns:

• Literals: hello matches the exact text "hello"
• Character classes: [aeiou] matches any vowel, \\d matches any digit
• Quantifiers: + (one or more), * (zero or more), {3} (exactly 3)
• Anchors: ^ matches start of line, $ matches end of line
• Groups: (abc) captures "abc" as a group, (?:abc) is non-capturing
• Alternation: cat|dog matches "cat" or "dog"

Common Regex Patterns

Email validation: [\\w.-]+@[\\w.-]+\\.\\w+

Phone number: \\(?\\d{3}\\)?[-.\\s]?\\d{3}[-.\\s]?\\d{4}

URL: https?://[\\w.-]+(/[\\w.-]*)*

IP address: \\b\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\b

Regex Flags Explained

• g (global): Find all matches, not just the first one
• i (case-insensitive): /hello/i matches "Hello", "HELLO", "hElLo"
• m (multiline): ^ and $ match at line boundaries, not just string start/end
• s (dotall): Makes . match newline characters too

Capture Groups

Parentheses create capture groups that extract parts of the match. For example, (\\d{4})-(\\d{2})-(\\d{2}) applied to "2024-01-15" captures "2024", "01", and "15" as separate groups. This tool displays group values for each match.

Privacy

All regex testing runs locally in your browser using JavaScript's native RegExp engine. No patterns or test data are transmitted to any server.

Process matched text with our Text Case Converter. Validate data formats with our JSON Validator.

Frequently asked questions

Do I need to add / delimiters?

No. Enter the pattern without delimiters. For example, enter \\d+ instead of /\\d+/g. Use the flag toggles to set flags.

What flags are available?

Global (g) finds all matches. Case-insensitive (i) ignores case. Multiline (m) makes ^ and $ match line boundaries. Dotall (s) makes . match newlines.

Does it show capture groups?

Yes. Each match displays its capture groups (if any) with group indices and values.

Is there a match limit?

Yes. The tool stops after 1,000 matches to prevent infinite loops with patterns that match empty strings.

Is my data private?

Yes. All regex testing runs in your browser. No data is sent to any server.

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