Pull capture groups from every match
Run a regex over sample text and get back a JSON array — one object per match, with numbered and named groups ready to paste anywhere. Runs locally.
[
{
"match": "alice@example.com",
"index": 0,
"groups": [
"alice",
"example.com"
],
"named": {
"user": "alice",
"domain": "example.com"
}
},
{
"match": "bob@test.org",
"index": 19,
"groups": [
"bob",
"test.org"
],
"named": {
"user": "bob",
"domain": "test.org"
}
},
{
"match": "carol@demo.io",
"index": 33,
"groups": [
"carol",
"demo.io"
],
"named": {
"user": "carol",
"domain": "demo.io"
}
}
]How to extract capture groups
Drop in a regex with groups, paste sample text, and get a JSON array — one object per match with all numbered and named groups.
- 01
Pattern with groups
Add () for unnamed groups or (?<name>...) for named ones. Both kinds extract.
Patterns compile through the JavaScript RegExp constructor, so syntax errors surface immediately and engine quirks like Unicode property escapes (\p{L}) work when the u flag is on.
patternECMAScriptliteralliveinput · literalregex · regex(?<user>\w+)@(?<domain>[\w.]+)loaded · ECMAScriptPCRE · ready - 02
Pick flags
Global flag g gives every match. Use i for case-insensitive matching.
Each flag character mirrors the ECMAScript literal: g enables iteration, i folds case, m anchors per line, s lets . match newlines, u unlocks proper Unicode, y is sticky, and d emits indices.
flagsoptionsg · i · mliveconfig · optionsflags · flagsgflags applied · liveECMA · live - 03
Read JSON
Each match becomes an object with match, index, groups, and named.
Watch for catastrophic backtracking on nested quantifiers — a common ReDoS source. The tool caps match counts to keep the page responsive on pathological patterns.
matchgroupshighlightReDoS-saferun · outputjson · matches[{"match":"alice@…","named":{"user":"alice","domain":"example.com"}}]matches · livegroups · live - 04
Copy or export
Grab the output as JSON, CSV, or plain text — ready for your editor or pipeline.
Copy writes via navigator.clipboard.writeText; downloads use a Blob and object URL, so nothing transits the network and the output is byte-identical to what you see on screen.
copyexportclipboardblobexport · exportedready · savedCopiedready to shipsuccess
Regex patterns that don't melt down
Use named groups
(?<year>\d{4}) reads better than $1 and survives reordering. Supported in ECMAScript 2018+.
Anchor strictly
Use ^/$ with the m flag when matching whole lines. Without anchors, partial matches sneak through.
Avoid catastrophic backtracking
Nested quantifiers like (a+)+ can explode. Run patterns through ReDoS Detector first.
Escape every literal
Backslash any meta character you want literally: \.\$\^\*\+\?\(\)\[\]\{\}\|\\.
Test edge cases
Empty string, single character, unicode, the maximum length you expect — write fixtures for each.
Patterns aren’t parsers
Don’t parse HTML, JSON, or balanced parens with regex. Use a proper parser when the grammar is recursive.
When to extract groups
Turn unstructured text into structured JSON.
Parse semi-structured logs
Pull dates, levels and messages with named groups. Compiles through the JavaScript RegExp constructor — engine quirks (Unicode property escapes, sticky matching, named groups) work when their flags are on. Error messages cite the exact position of any syntax issue.
ReDoS-safeScrape lists
Turn a paste of `name <email>` into a JSON array. Pairs with the ReDoS detector to catch catastrophic backtracking before you deploy. A pattern that handles 1k-character input fine can become a denial-of-service vector on attacker-controlled 1M-character input.
ECMA-compliantBuild a data pipeline
Use the JSON output as upstream input. Output exports as JavaScript, Python re, Java util.regex, .NET System.Text.RegularExpressions, PCRE, and POSIX — language quirks are highlighted on conversion so you don't ship a JS-only pattern to a Go service.
spec-gradeVerify a pattern
Eyeball the extracted groups before shipping a regex. Capture groups (named or numbered) round-trip cleanly into replacement strings, JSON output, or CSV extraction without re-typing. Backreferences ($1, ${name}) preserve semantics across languages.
cross-engineAuthor documentation
Show example matches and their groups in docs. Test against edge cases — empty input, single character, max length, multibyte boundaries — to catch off-by-one and zero-length match bugs before they reach production.
test-readyQuickly tokenise
Faster than writing a parser for an ad-hoc format. All matching runs client-side so secret patterns never leave the browser. Useful when the pattern itself is sensitive (PII regexes, internal data formats, security filters).
production-readyFrequently asked questions
Something missing?
Tell us what you need. We ship the top requests every two weeks.