Which regex flavor does this use?

JavaScript. Patterns run through your browser's own RegExp engine, which is V8 in Chrome and Edge, JavaScriptCore in Safari, and SpiderMonkey in Firefox. What matches here is what will match in your JS code.

Which flags are supported?

All six that JavaScript accepts: g (global), i (case insensitive), m (multiline), s (dotAll), u (unicode), and y (sticky).

What works in PCRE but throws in JavaScript?

Possessive quantifiers (a++, a*+) and atomic groups (?>...) are not valid JavaScript and throw a SyntaxError. The \A and \z anchors do not exist either; use ^ and $ instead. Recursion (?R) and inline flag scoping (?i) are also unsupported. Lookbehind does work in modern browsers, but it is newer than lookahead, so check your target if you support older ones.

What regex flags are supported?

Global (g), case-insensitive (i), multiline (m), dotAll (s), unicode (u), and sticky (y).

Does it support capture groups?

Yes. Named and numbered capture groups are displayed for each match.

Can I use it for find-and-replace?

Yes. Switch to Replace mode to preview substitutions including $1, $2 references.

Regex Tester: JavaScript (V8) Flavor, Online

Test and debug regular expressions with live highlighting, replace mode, and a pattern library.

✦ FreeNo SignupInstantText Regular Expressions Guide

Regular Expression

//gi

FlagsJavaScript (V8) flavor

Test String

Matches (2)

Match List

hello@buildutilities.comsupport@example.org

Example

Input

Pattern: (\d{4})-(\d{2})-(\d{2})
Test: 2024-01-15

Output

Match: 2024-01-15
$1: 2024, $2: 01, $3: 15

The regex matches a date format and captures year, month, and day in separate groups.

How to Use Regex Tester

1
Enter Pattern
Type your regular expression in the pattern field.
2
Add Test String
Paste the text you want to test against.
3
View Matches
Matches are highlighted in real time. Use Replace mode for substitution preview.

What is Regex Tester?

The Regex Tester provides live match highlighting, capture group inspection, replace mode with substitution preview, a library of common patterns (email, URL, IP, etc.), and an interactive cheat sheet. All processing happens in your browser using JavaScript's native RegExp engine.

Common Use Cases

✦Building and debugging data validation patterns
✦Extracting structured data from log files
✦Testing URL routing patterns for web frameworks
✦Previewing search-and-replace transformations

Frequently Asked Questions

Also available as

Online Regex Tester Free Regex Tester Regex Test Tool

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