Regex Tester

About the Regex Tester

Regular expressions (regex) are powerful pattern-matching tools used to search, validate, and manipulate text. They're essential for form validation, data extraction, log parsing, and text processing. Our Regex Tester lets you build and test regex patterns against sample text in real time. See all matches highlighted instantly, with support for common flags like global (g), case-insensitive (i), and multiline (m).

What Is Regex Tester?

A regular expression is a compact language for describing patterns in text. It combines literal characters (which match themselves) with metacharacters that encode rules: '.' matches any character, '*' repeats the previous token zero or more times, '+' repeats one or more times, '?' makes a token optional, '[...]' defines a character set, '(...)' captures a group, and '\' escapes a metacharacter or starts a shorthand like '\d' (digit) or '\s' (whitespace). Anchors like '^' and '$' match positions rather than characters. Regex engines are built into virtually every programming language and many tools (grep, sed, editors), but small differences in syntax and features exist between engines — the JavaScript engine used by this tool follows the ECMAScript specification. Mastering regex pays off across validation, parsing, search-and-replace, and log analysis.

How to Use

1. Enter your regex pattern in the pattern input field above.
2. Optionally add flags (g for global, i for case-insensitive, m for multiline).
3. Paste the text you want to test against in the textarea.
4. Matches are displayed in real time as you type.
5. View the total match count and a list of all captured groups.

Common Use Cases

• Validating email addresses, phone numbers, and other structured input in forms
• Extracting fields such as dates, IDs, or prices from unstructured log lines
• Building find-and-replace rules in editors or data-cleaning scripts
• Parsing configuration files and tokenizing source code
• Testing patterns before deploying them to production validation logic

Examples

Pattern: \b\w+@\w+\.\w+\b  on: 'contact me at jane@example.com'

Match: jane@example.com

Tips & Best Practices

• Use parentheses () to create capture groups for extracting specific parts of a match.
• The dot . matches any character except newline. Use [\s\S] to match truly any character.
• Regex101.com is another tool for deep regex analysis — use ours for quick, privacy-focused testing.
• Common patterns: \d+ for numbers, [A-Za-z]+ for words, ^ for start, $ for end of line.

Frequently Asked Questions