Which regex flavour is used?

The tester uses JavaScript's built-in RegExp engine, which follows the ECMAScript specification. This matches the behaviour you get in Node.js, browsers, and most frontend frameworks.

Are capture groups shown?

Yes. Each match is listed with its position, and any capture groups within that match are shown as sub-items.

What flags are available?

g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), s (dotAll — . matches newlines), and u (Unicode mode) are all supported.

What does the live update mean?

As you type the pattern or the test text, matches are recalculated immediately without needing to click a button.

How do I match a literal dot or plus sign?

Escape special regex characters with a backslash: \. matches a literal dot, \+ matches a plus, \* matches an asterisk, $ and $ match parentheses. Or use a character class [.] to match a literal dot.

What is the difference between + and * in regex?

+ matches one or more occurrences; * matches zero or more. So \d+ requires at least one digit, while \d* would also match an empty string. Use + when the pattern must appear at least once.

Regex Tester

The Regex Tester lets you write a regular expression and test it against sample text with live match highlighting. All JavaScript regex flags are supported (g, i, m, s, u). Matches are highlighted in the test text, captured groups are listed separately, and any regex syntax errors are displayed immediately.

Runs entirely in your browser — your input is never uploaded, stored, or logged.

Debug and validate regular expressions quickly without needing a code editor or a Node.js REPL. To extract all matches from text using a pattern, use the Regex Matches Extractor.

How to Use

1Enter your regular expression in the pattern field.
2Add optional flags: global, case-insensitive, multiline.
3Paste your test text — matches highlight in real-time.
4View individual matches and capture group values below.

Common Uses

→Test and debug a regular expression against sample text
→Find which parts of a string a pattern matches
→Verify a regex works correctly before adding it to code
→Explore match groups and capture groups visually

Examples

Email pattern

Input

Pattern: [\w.-]+@[\w-]+\.[a-z]{2,}
Text: Contact alice@example.com or bob@test.org

Output

2 matches: alice@example.com, bob@test.org

Frequently Asked Questions

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