What is a named capture group in regex?

A named capture group uses the syntax (? ...) to assign a label to a captured group. Instead of $1 or match[1], you reference the value by name: match.groups.name or $ in replacements.

How do I extract a named group in JavaScript?

Use const m = text.match(/(? \d{4})-(? \d{2})/); then m.groups.year and m.groups.month. With the g flag use regex.exec() in a loop and access exec_result.groups.

Can I use named groups in replace?

Yes. Use $ in the replacement string: '2024-01'.replace(/(? \d{4})-(? \d{2})/, '$ /$ ') produces '01/2024'.

Do named groups work in lookbehind?

Yes. (? \w+):) is valid. Named groups inside lookbehinds are captured but the position is before the match, so they appear in match.groups normally.

Flowfiles ← Regex Tester

Regex Named Capture Groups

Test (?<name>…) patterns · Extract labeled values · Replace with $<name> — free, no signup

Named capture groups let you label parts of a regex pattern and retrieve them by name instead of index. Test them live with our online regex tester — group values appear labeled in the match panel.

Test named capture groups right now — paste your pattern and see each group extracted by name.

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Named groups syntax and examples

A named capture group uses (?<name>…). The name must start with a letter and contain only letters, digits, or underscores. You can have multiple named groups in the same pattern.

// Extract date parts

const re = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;

const m = '2024-03-15'.match(re);

console.log(m.groups.year);  // "2024"

console.log(m.groups.month); // "03"

console.log(m.groups.day);   // "15"

In Replace mode, use $<name> to reference the group:

'2024-03-15'.replace(/(?<y>\d{4})-(?<m>\d{2})-(?<d>\d{2})/, '$<d>/$<m>/$<y>')

// → "15/03/2024"

With the g flag, iterate with matchAll():

const text = 'foo@a.com bar@b.org';

const re = /(?<user>[\w.]+)@(?<domain>[\w.]+)/g;

for (const m of text.matchAll(re)) {

  console.log(m.groups.user, m.groups.domain);

}

Frequently asked questions

What is a named capture group?

A named capture group assigns a label to a capturing group using (?<name>…). Values are accessible via match.groups.name instead of by index. This makes patterns more readable and refactoring safer.

Are named groups available in all browsers?

Yes. Named capture groups were introduced in ES2018 and are supported in all modern browsers (Chrome 64+, Firefox 78+, Safari 11.1+, Edge 79+).

Can two groups share the same name?

In ECMAScript 2025+, duplicate named groups are allowed in alternations ((?<x>a)|(?<x>b)). In older engines this throws a SyntaxError, so avoid duplicates for broad compatibility.

How do I use named groups with replaceAll?

String.prototype.replaceAll() with a regex requires the g flag. The replacement string syntax is the same: $<name>. You can also pass a function as the second argument and access match.groups in it.

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