HTML 的 lang 屬性可用于聲明網頁或部分網頁的語言，這對搜尋引擎和浏覽器是有幫助的。
根據 W3C 推薦标準，您應該通過 <html> 标簽中的 lang 屬性對每張頁面中的主要語言進行聲明：
比如聲明原文版語言：
<html lang="en">
...
</html>
在 XHTML 中，采用如下方式在 <html> 标簽中對語言進行聲明：
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
ISO 639-1 為各種語言定義了縮略詞。您可以在 HTML 和 XHTML 中的 lang 和 xml:lang 屬性中使用它們。
語言
ISO 代碼
Abkhazian
ab
Afar
aa
Afrikaans
af
Albanian
sq
Amharic
am
Arabic
ar
Aragonese
an
Armenian
hy
Assamese
as
Aymara
ay
Azerbaijani
az
Bashkir
ba
Basque
eu
Bengali (Bangla)
bn
Bhutani
dz
Bihari
bh
Bislama
bi
Breton
br
Bulgarian
bg
Burmese
my
Byelorussian (Belarusian)
be
Cambodian
km
Catalan
ca
Cherokee
Chewa
Chinese (簡體)
zh
Chinese (繁體)
Corsican
co
Croatian
hr
Czech
cs
Danish
da
Divehi
Dutch
nl
Edo
English
en
Esperanto
eo
Estonian
et
Faeroese
fo
Farsi
fa
Fiji
fj
Finnish
fi
Flemish
French
fr
Frisian
fy
Fulfulde
Galician
gl
Gaelic (Scottish)
gd
Gaelic (Manx)
gv
Georgian
ka
German
de
Greek
el
Greenlandic
kl
Guarani
gn
Gujarati
gu
Haitian Creole
ht
Hausa
ha
Hawaiian
Hebrew
he, iw
Hindi
hi
Hungarian
hu
Ibibio
Icelandic
is
Ido
io
Igbo
Indonesian
id, in
Interlingua
ia
Interlingue
ie
Inuktitut
iu
Inupiak
ik
Irish
ga
Italian
it
Japanese
ja
Javanese
jv
Kannada
kn
Kanuri
Kashmiri
ks
Kazakh
kk
Kinyarwanda (Ruanda)
rw
Kirghiz
ky
Kirundi (Rundi)
rn
Konkani
Korean
ko
Kurdish
ku
Laothian
lo
Latin
la
Latvian (Lettish)
lv
Limburgish ( Limburger)
li
Lingala
ln
Lithuanian
lt
Macedonian
mk
Malagasy
mg
Malay
ms
Malayalam
ml
Maltese
mt
Maori
mi
Marathi
mr
Moldavian
mo
Mongolian
mn
Nauru
na
Nepali
ne
Norwegian
no
Occitan
oc
Oriya
or
Oromo (Afaan Oromo)
om
Papiamentu
Pashto (Pushto)
ps
Polish
pl
Portuguese
pt
Punjabi
pa
Quechua
qu
Rhaeto-Romance
rm
Romanian
ro
Russian
ru
Sami (Lappish)
Samoan
sm
Sangro
sg
Sanskrit
sa
Serbian
sr
Serbo-Croatian
sh
Sesotho
st
Setswana
tn
Shona
sn
Sichuan Yi
ii
Sindhi
sd
Sinhalese
si
Siswati
ss
Slovak
sk
Slovenian
sl
Somali
so
Spanish
es
Sundanese
su
Swahili (Kiswahili)
sw
Swedish
sv
Syriac
Tagalog
tl
Tajik
tg
Tamazight
Tamil
ta
Tatar
tt
Telugu
te
Thai
th
Tibetan
bo
Tigrinya
ti
Tonga
to
Tsonga
ts
Turkish
tr
Turkmen
tk
Twi
tw
Uighur
ug
Ukrainian
uk
Urdu
ur
Uzbek
uz
Venda
Vietnamese
vi
Volapük
vo
Wallon
wa
Welsh
cy
Wolof
wo
Xhosa
xh
Yi
Yiddish
yi, ji
Yoruba
yo
Zulu
zu