/flags /regex/javascript-regex-flags

JavaScript regex flags: g, i, m, s, u, v, y and d

updated 2026-10-20

tool: Regex
command: /pattern/flags or new RegExp(pattern, flags)
flag: g i m s u v y d
default: none

Flags go after the closing slash, /pattern/gi, or as the second argument of new RegExp(pattern, "gi"). They change how the whole pattern matches; JavaScript has no inline flags such as (?i) for the whole pattern.

Each flag, run in Node.js

bash

node - <<'EOF'
console.log("node", process.version);
const show = (label, value) => console.log(label.padEnd(30), JSON.stringify(value));
show("no flag   'a1 b2'.match(/\\d/)", "a1 b2".match(/\d/)[0]);
show("g         match(/\\d/g)", "a1 b2".match(/\d/g));
show("i         /hello/i.test('HeLLo')", /hello/i.test("HeLLo"));
show("m         'a\\nb'.match(/^b/m)", "a\nb".match(/^b/m)?.[0]);
show("(no m)    'a\\nb'.match(/^b/)", "a\nb".match(/^b/));
show("s         /a.b/s.test('a\\nb')", /a.b/s.test("a\nb"));
show("(no s)    /a.b/.test('a\\nb')", /a.b/.test("a\nb"));
show("u         '😀'.match(/./u)", "😀".match(/./u)[0]);
show("(no u)    '😀'.match(/./)[0].length", "😀".match(/./)[0].length);
show("u         /\\p{L}+/u on 'café'", "café".match(/\p{L}+/u)[0]);
show("v         /[\\p{L}--[a-z]]/v on 'aÉb'", "aÉb".match(/[\p{L}--[a-z]]/v)[0]);
const y = /\d/y; y.lastIndex = 1;
show("y         /\\d/y at lastIndex 1 of 'a1'", y.exec("a1")?.[0]);
show("d         /b+/d indices on 'abbc'", /b+/d.exec("abbc").indices[0]);
EOF

Output

node v24.20.0
no flag   'a1 b2'.match(/\d/)  "1"
g         match(/\d/g)         ["1","2"]
i         /hello/i.test('HeLLo') true
m         'a\nb'.match(/^b/m)  "b"
(no m)    'a\nb'.match(/^b/)   null
s         /a.b/s.test('a\nb')  true
(no s)    /a.b/.test('a\nb')   false
u         '😀'.match(/./u)     "😀"
(no u)    '😀'.match(/./)[0].length 1
u         /\p{L}+/u on 'café'  "café"
v         /[\p{L}--[a-z]]/v on 'aÉb' "É"
y         /\d/y at lastIndex 1 of 'a1' "1"
d         /b+/d indices on 'abbc' [1,3]

Summary

Flag	Name	Effect
g	global	find all matches; needed for matchAll and replaceAll with a regex
i	ignoreCase	case-insensitive
m	multiline	^ and $ match at line breaks, not only at the start and end of the string
s	dotAll	. also matches line terminators
u	unicode	code points instead of UTF-16 units, \p{…} property escapes, stricter syntax
v	unicodeSets	everything u does plus set operations ([A--B], [A&&B]) and string properties
y	sticky	match only at lastIndex
d	hasIndices	add start and end indices of each group to the result

Sources

cheat sheets · regexRegex cheat sheet: characters, quantifiers, groups and lookaroundsRegex cheat sheet: character classes, anchors, quantifiers, greedy and lazy matching, groups and backreferences, lookarounds, with tested Python examples.compat · regexRegex features by engine: JavaScript, Python, PCRE and POSIX EREWhich regex features work where: lookbehind, named groups, \p{L}, atomic groups and possessive quantifiers in JavaScript, Python re, PCRE and POSIX ERE, tested.glossary · regexGreedy vs lazy quantifiers in regexA greedy quantifier such as .* matches as much as it can and backtracks only when needed; a lazy one such as .*? matches as little as possible. Examples.

Each flag, run in Node.js

Summary

Sources

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