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Regex Tester & Debugger

Test regular expressions with real-time match highlighting, capture groups, pattern explanation, and a complete cheat sheet. Uses the JavaScript regex engine — 100% client-side.

//g
Flags:2 matches
Quick Insert

Match Highlighting

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Match Results

2 matches
Match 1Index: 14
[email protected]
Capture Groups
Group 1hello
Group 2example.com
Match 2Index: 35
[email protected]
Capture Groups
Group 1support
Group 2devtools.page

Regex to English

Plain EnglishFind a pattern involving word characters, with 2 capture groups — all occurrences (global).

Token-by-Token Breakdown

(Start capture group
\wMatch any word character [a-zA-Z0-9_]
+Match 1 or more of the preceding token
)End group
@Match literal "@"
(Start capture group
\wMatch any word character [a-zA-Z0-9_]
+Match 1 or more of the preceding token
\.Match literal "."
\wMatch any word character [a-zA-Z0-9_]
+Match 1 or more of the preceding token
)End group

Regex Library

20 ready-to-use patterns

Cheat Sheet

Frequently Asked Questions

What is a regular expression (regex)?

A regular expression (regex) is a sequence of characters that defines a search pattern. Regex is used in programming for tasks like string matching, validation, search-and-replace, and data extraction. Most programming languages support regex natively.

What regex engine does this tester use?

This tool uses the JavaScript (ECMAScript) RegExp engine built into your browser. It supports all standard regex features including lookahead, lookbehind, named capture groups, and Unicode mode. All processing runs client-side — no data is sent to any server.

What do the regex flags (g, i, m, s, u) mean?

g (global) finds all matches instead of stopping after the first. i (case-insensitive) ignores letter case. m (multiline) makes ^ and $ match line boundaries. s (dotall) makes . match newline characters. u (unicode) enables full Unicode matching including surrogate pairs.

How do capture groups work in regex?

Capture groups are created with parentheses (). They extract specific parts of a match. For example, (\d{4})-(\d{2})-(\d{2}) matching "2024-03-15" captures three groups: "2024", "03", and "15". Named groups use (?<name>...) syntax for clearer code.

Is my data safe when using this regex tester?

Yes. All regex matching is performed entirely in your browser using JavaScript's built-in RegExp engine. No data is transmitted to any server. Your patterns and test strings never leave your device.

Can I test multiline strings?

Yes. The test string input supports multiline text. Enable the "m" (multiline) flag to make ^ and $ match the start and end of each line rather than the entire string. Enable the "s" (dotall) flag to make . match newline characters.