What is the difference between ISO 639-1 and ISO 639-2 language codes?

ISO 639-1 defines two-letter codes (like "en" for English, "fr" for French, "zh" for Chinese) for 184 of the most widely used languages. ISO 639-2 defines three-letter codes for a broader set of over 500 languages. Most web and software contexts use ISO 639-1 codes, often combined with a region subtag (e.g. "en-US", "zh-TW") to form a BCP 47 language tag.

Where are language codes used in web development?

Language codes appear in: the HTML lang attribute ( ), the HTTP Content-Language and Accept-Language headers, the tag, hreflang attributes for international SEO, JavaScript's Intl API for locale-aware formatting, and i18n libraries like i18next and vue-i18n.

What language code should I use for Chinese — zh, zh-CN, or zh-TW?

"zh" identifies the Chinese language in general. "zh-CN" specifies Simplified Chinese as used in mainland China. "zh-TW" specifies Traditional Chinese as used in Taiwan. Use "zh-CN" or "zh-TW" whenever you need to distinguish between the two writing systems, as they use different character sets and fonts.

ISO 639 Language Codes

Two- and three-letter language codes with native and English names, for locale and hreflang work.

180 languages

639-1	639-2	Language	Native Name	Script
aa	aar	Afar	Afaraf	Latin
ab	abk	Abkhazian	Аҧсшәа	Cyrillic
af	afr	Afrikaans	Afrikaans	Latin
ak	aka	Akan	Akan	Latin
am	amh	Amharic	አማርኛ	Ethiopic
ar	ara	Arabic	العربية	Arabic
as	asm	Assamese	অসমীয়া	Bengali
av	ava	Avaric	авар мацӀ	Cyrillic
ay	aym	Aymara	aymar aru	Latin
az	aze	Azerbaijani	azərbaycan dili	Latin
ba	bak	Bashkir	башҡорт теле	Cyrillic
be	bel	Belarusian	беларуская мова	Cyrillic
bg	bul	Bulgarian	български език	Cyrillic
bh	bih	Bihari	भोजपुरी	Devanagari
bi	bis	Bislama	Bislama	Latin
bm	bam	Bambara	bamanankan	Latin
bn	ben	Bengali	বাংলা	Bengali
bo	tib	Tibetan	བོད་ཡིག	Tibetan
br	bre	Breton	brezhoneg	Latin
bs	bos	Bosnian	bosanski jezik	Latin
ca	cat	Catalan	Català	Latin
ce	che	Chechen	нохчийн мотт	Cyrillic
ch	cha	Chamorro	Chamoru	Latin
co	cos	Corsican	corsu	Latin
cs	cze	Czech	čeština	Latin
cu	chu	Church Slavic	ѩзыкъ словѣньскъ	Cyrillic
cv	chv	Chuvash	чӑваш чӗлхи	Cyrillic
cy	wel	Welsh	Cymraeg	Latin
da	dan	Danish	dansk	Latin
de	ger	German	Deutsch	Latin
dv	div	Divehi	Dhivehi	Thaana
dz	dzo	Dzongkha	རྫོང་ཁ	Tibetan
ee	ewe	Ewe	Eʋegbe	Latin
el	gre	Greek	Ελληνικά	Greek
en	eng	English	English	Latin
eo	epo	Esperanto	Esperanto	Latin
es	spa	Spanish	Español	Latin
et	est	Estonian	eesti keel	Latin
eu	baq	Basque	euskara	Latin
fa	per	Persian	فارسی	Arabic
ff	ful	Fula	Fulfulde	Latin
fi	fin	Finnish	suomen kieli	Latin
fj	fij	Fijian	Vakaviti	Latin
fo	fao	Faroese	føroyskt	Latin
fr	fre	French	Français	Latin
fy	fry	West Frisian	Frysk	Latin
ga	gle	Irish	Gaeilge	Latin
gd	gla	Scottish Gaelic	Gàidhlig	Latin
gl	glg	Galician	Galego	Latin
gn	grn	Guaraní	Avañe'ẽ	Latin
gu	guj	Gujarati	ગુજરાતી	Gujarati
gv	glv	Manx	Gaelg	Latin
ha	hau	Hausa	هَوُسَ	Arabic
he	heb	Hebrew	עברית	Hebrew
hi	hin	Hindi	हिन्दी	Devanagari
ho	hmo	Hiri Motu	Hiri Motu	Latin
hr	hrv	Croatian	Hrvatski	Latin
ht	hat	Haitian Creole	Kreyòl ayisyen	Latin
hu	hun	Hungarian	Magyar	Latin
hy	arm	Armenian	Հայերեն	Armenian
hz	her	Herero	Otjiherero	Latin
ia	ina	Interlingua	Interlingua	Latin
id	ind	Indonesian	Bahasa Indonesia	Latin
ig	ibo	Igbo	Asụsụ Igbo	Latin
ii	iii	Sichuan Yi	ꆈꌠ꒿	Yi
ik	ipk	Inupiaq	Iñupiaq	Latin
io	ido	Ido	Ido	Latin
is	ice	Icelandic	Íslenska	Latin
it	ita	Italian	Italiano	Latin
iu	iku	Inuktitut	ᐃᓄᒃᑎᑐᑦ	Canadian Aboriginal
ja	jpn	Japanese	日本語	Japanese
jv	jav	Javanese	ꦧꦱꦗꦮ	Javanese
ka	geo	Georgian	ქართული	Georgian
kg	kon	Kongo	Kikongo	Latin
ki	kik	Kikuyu	Gĩkũyũ	Latin
kj	kua	Kwanyama	Kuanyama	Latin
kk	kaz	Kazakh	қазақ тілі	Cyrillic
kl	kal	Kalaallisut	kalaallisut	Latin
km	khm	Khmer	ភាសាខ្មែរ	Khmer
kn	kan	Kannada	ಕನ್ನಡ	Kannada
ko	kor	Korean	한국어	Hangul
kr	kau	Kanuri	Kanuri	Latin
ks	kas	Kashmiri	कश्मीरी	Devanagari
ku	kur	Kurdish	Kurdî	Latin
kv	kom	Komi	коми кыв	Cyrillic
kw	cor	Cornish	Kernewek	Latin
ky	kir	Kyrgyz	Кыргызча	Cyrillic
la	lat	Latin	latine	Latin
lb	ltz	Luxembourgish	Lëtzebuergesch	Latin
lg	lug	Ganda	Luganda	Latin
li	lim	Limburgan	Limburgs	Latin
ln	lin	Lingala	Lingála	Latin
lo	lao	Lao	ພາສາລາວ	Lao
lt	lit	Lithuanian	Lietuvių kalba	Latin
lu	lub	Luba-Katanga	Tshiluba	Latin
lv	lav	Latvian	Latviešu valoda	Latin
mg	mlg	Malagasy	Fiteny malagasy	Latin
mh	mah	Marshallese	Kajin M̧ajeļ	Latin
mi	mao	Māori	te reo Māori	Latin
mk	mac	Macedonian	Македонски јазик	Cyrillic
ml	mal	Malayalam	മലയാളം	Malayalam
mn	mon	Mongolian	Монгол хэл	Cyrillic
mr	mar	Marathi	मराठी	Devanagari
ms	may	Malay	Bahasa Melayu	Latin
mt	mlt	Maltese	Malti	Latin
my	bur	Burmese	ဗမာစာ	Myanmar
na	nau	Nauru	Ekakairũ Naoero	Latin
nb	nob	Norwegian Bokmål	Norsk Bokmål	Latin
nd	nde	North Ndebele	isiNdebele	Latin
ne	nep	Nepali	नेपाली	Devanagari
ng	ndo	Ndonga	Owambo	Latin
nl	dut	Dutch	Nederlands	Latin
nn	nno	Norwegian Nynorsk	Norsk Nynorsk	Latin
no	nor	Norwegian	Norsk	Latin
nr	nbl	South Ndebele	isiNdebele	Latin
nv	nav	Navajo	Diné bizaad	Latin
ny	nya	Chichewa	chiCheŵa	Latin
oc	oci	Occitan	Occitan	Latin
oj	oji	Ojibwe	ᐊᓂᔑᓈᐯᒧᐎᓐ	Canadian Aboriginal
om	orm	Oromo	Afaan Oromoo	Latin
or	ori	Odia	ଓଡ଼ିଆ	Odia
os	oss	Ossetic	ирон æвзаг	Cyrillic
pa	pan	Punjabi	ਪੰਜਾਬੀ	Gurmukhi
pi	pli	Pāli	पाऴि	Devanagari
pl	pol	Polish	Polski	Latin
ps	pus	Pashto	پښتو	Arabic
pt	por	Portuguese	Português	Latin
qu	que	Quechua	Runa Simi	Latin
rm	roh	Romansh	Rumantsch Grischun	Latin
rn	run	Kirundi	Ikirundi	Latin
ro	rum	Romanian	Română	Latin
ru	rus	Russian	Русский	Cyrillic
rw	kin	Kinyarwanda	Ikinyarwanda	Latin
sa	san	Sanskrit	संस्कृतम्	Devanagari
sc	srd	Sardinian	sardu	Latin
sd	snd	Sindhi	सिन्धी	Devanagari
se	sme	Northern Sami	Davvisámegiella	Latin
sg	sag	Sango	yângâ tî sängö	Latin
si	sin	Sinhala	සිංහල	Sinhala
sk	slo	Slovak	Slovenčina	Latin
sl	slv	Slovenian	Slovenščina	Latin
sm	smo	Samoan	gagana fa'a Samoa	Latin
sn	sna	Shona	chiShona	Latin
so	som	Somali	Soomaaliga	Latin
sq	alb	Albanian	Shqip	Latin
sr	srp	Serbian	српски	Cyrillic
ss	ssw	Swati	SiSwati	Latin
st	sot	Southern Sotho	Sesotho	Latin
su	sun	Sundanese	Basa Sunda	Latin
sv	swe	Swedish	Svenska	Latin
sw	swa	Swahili	Kiswahili	Latin
ta	tam	Tamil	தமிழ்	Tamil
te	tel	Telugu	తెలుగు	Telugu
tg	tgk	Tajik	тоҷикӣ	Cyrillic
th	tha	Thai	ไทย	Thai
ti	tir	Tigrinya	ትግርኛ	Ethiopic
tk	tuk	Turkmen	Türkmen	Latin
tl	tgl	Tagalog	Wikang Tagalog	Latin
tn	tsn	Tswana	Setswana	Latin
to	ton	Tongan	Faka Tonga	Latin
tr	tur	Turkish	Türkçe	Latin
ts	tso	Tsonga	Xitsonga	Latin
tt	tat	Tatar	татар теле	Cyrillic
tw	twi	Twi	Twi	Latin
ty	tah	Tahitian	Reo Tahiti	Latin
ug	uig	Uyghur	ئۇيغۇرچە‎	Arabic
uk	ukr	Ukrainian	Українська	Cyrillic
ur	urd	Urdu	اردو	Arabic
uz	uzb	Uzbek	O'zbek	Latin
ve	ven	Venda	Tshivenḓa	Latin
vi	vie	Vietnamese	Tiếng Việt	Latin
vo	vol	Volapük	Volapük	Latin
wa	wln	Walloon	Walon	Latin
wo	wol	Wolof	Wollof	Latin
xh	xho	Xhosa	isiXhosa	Latin
yi	yid	Yiddish	ייִדיש	Hebrew
yo	yor	Yoruba	Yorùbá	Latin
za	zha	Zhuang	Saɯ cueŋƅ	Latin
zh	zho	Chinese	中文	Chinese
zu	zul	Zulu	isiZulu	Latin

Language tags are more than a language code

BCP 47 defines the full syntax used by HTML lang, hreflang, Accept-Language and Intl APIs. The parts, in order:

Language (required) —ISO 639-1 two-letter where one exists (en, fr, zh), otherwise 639-2/3 three-letter (haw, fil).
Script —Four letters, title case. Needed when a language is written in more than one script: zh-Hans (simplified) versus zh-Hant (traditional), sr-Latn versus sr-Cyrl.
Region —Two-letter ISO 3166 country code, uppercase. en-GB, en-US, pt-BR, pt-PT. This is what distinguishes spelling, date formats and vocabulary.
Variant and extensions —Rarely needed. de-CH-1901 for pre-reform Swiss German orthography; -u- extensions carry locale preferences such as calendar and numbering system.

hreflang rules that trip people up

If you serve the same content in several languages or regions, hreflang tells search engines which version to show whom. Three rules cause most implementation failures:

It must be reciprocal. If page A declares B as its French alternate, B must declare A as its English alternate. One-directional annotations are ignored entirely.

Every page must reference itself. The set of hreflang tags on a page includes a self-referential entry. Omitting it invalidates the whole cluster.

The region subtag is a region, not a language. en-GB means English as used in Great Britain. There is no such thing as en-UK in this context, because the ISO country code is GB.

Add x-default for the fallback page shown when no declared locale matches — usually a language selector or your primary market's version. Note that CodeLint.Dev itself does not use hreflang: language switching here is client-side on a single URL set, so there are no per-language URLs to annotate.

About

The Language Codes reference covers all ISO 639-1 two-letter and ISO 639-2 three-letter language codes along with the native name of each language, the English name, and the primary writing script. This is the go-to reference for internationalisation (i18n), locale configuration, HTTP Accept-Language headers, and language selection in applications.

How to use

1 Search by language name or code (e.g. "French" or "fr").
2 Filter by script (Latin, Cyrillic, Arabic, etc.) using the dropdown.
3 Click any row to copy the ISO 639-1 or ISO 639-2 code.

What is the difference between ISO 639-1 and ISO 639-2 language codes?: ISO 639-1 defines two-letter codes (like "en" for English, "fr" for French, "zh" for Chinese) for 184 of the most widely used languages. ISO 639-2 defines three-letter codes for a broader set of over 500 languages. Most web and software contexts use ISO 639-1 codes, often combined with a region subtag (e.g. "en-US", "zh-TW") to form a BCP 47 language tag.
Where are language codes used in web development?: Language codes appear in: the HTML lang attribute (<html lang="en">), the HTTP Content-Language and Accept-Language headers, the <meta name="content-language"> tag, hreflang attributes for international SEO, JavaScript's Intl API for locale-aware formatting, and i18n libraries like i18next and vue-i18n.
What language code should I use for Chinese — zh, zh-CN, or zh-TW?: "zh" identifies the Chinese language in general. "zh-CN" specifies Simplified Chinese as used in mainland China. "zh-TW" specifies Traditional Chinese as used in Taiwan. Use "zh-CN" or "zh-TW" whenever you need to distinguish between the two writing systems, as they use different character sets and fonts.

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