When running multiple international Websites, is the best practice in language tags to specify firstly the language code then the country code, or vice versa?
For instance:
http://www.example.com/en-in/ (English, India) or https://www.example.com/in-en/
The typical format for a locale is comprised of the two letter language code followed by the two letter country code. For example, here is a list of all the locales supported by Java:
Language Country Locale ID
--------------------------------------------------------------
Albanian Albania sq_AL
Arabic Algeria ar_DZ
Arabic Bahrain ar_BH
Arabic Egypt ar_EG
Arabic Iraq ar_IQ
Arabic Jordan ar_JO
Arabic Kuwait ar_KW
Arabic Lebanon ar_LB
Arabic Libya ar_LY
Arabic Morocco ar_MA
Arabic Oman ar_OM
Arabic Qatar ar_QA
Arabic Saudi Arabia ar_SA
Arabic Sudan ar_SD
Arabic Syria ar_SY
Arabic Tunisia ar_TN
Arabic United Arab Emirates ar_AE
Arabic Yemen ar_YE
Belarusian Belarus be_BY
Bulgarian Bulgaria bg_BG
Catalan Spain ca_ES
Chinese (Simplified) China zh_CN
Chinese (Simplified) Singapore zh_SG
Chinese (Traditional) Hong Kong zh_HK
Chinese (Traditional) Taiwan zh_TW
Croatian Croatia hr_HR
Czech Czech Republic cs_CZ
Danish Denmark da_DK
Dutch Belgium nl_BE
Dutch Netherlands nl_NL
English Australia en_AU
English Canada en_CA
English India en_IN
English Ireland en_IE
English Malta en_MT
English New Zealand en_NZ
English Philippines en_PH
English Singapore en_SG
English South Africa en_ZA
English United Kingdom en_GB
English United States en_US
Estonian Estonia et_EE
Finnish Finland fi_FI
French Belgium fr_BE
French Canada fr_CA
French France fr_FR
French Luxembourg fr_LU
French Switzerland fr_CH
German Austria de_AT
German Germany de_DE
German Luxembourg de_LU
German Switzerland de_CH
Greek Cyprus el_CY
Greek Greece el_GR
Hebrew Israel iw_IL
Hindi India hi_IN
Hungarian Hungary hu_HU
Icelandic Iceland is_IS
Indonesian Indonesia in_ID
Irish Ireland ga_IE
Italian Italy it_IT
Italian Switzerland it_CH
Japanese (Gregorian calendar) Japan ja_JP
Japanese (Imperial calendar) Japan ja_JP_JP
Korean South Korea ko_KR
Latvian Latvia lv_LV
Lithuanian Lithuania lt_LT
Macedonian Macedonia mk_MK
Malay Malaysia ms_MY
Maltese Malta mt_MT
...
When used on the web, the W3C recommends using a dash rather than an underscore as the canonical form. That document still shows examples with the capitalized language identifier as canonical, but specifies that all lowercase would match. For the purposes of URLs, I would use all lower case with a hyphen.
This is the language which dominates because there are many countries which use the same language. That's why, you need to specify to language first and then precise with the country.
Thus, the most appropriate is http://www.example.com/en-in/.
However, there is no impact on SEO, it's just a standard.
For this kind of stuff, you can just take a look how big companies do. For instance, Facebook has URLs like:
https://fr-ca.facebook.com (for Canadians who speak French)https://fr-fr.facebook.com (for French people who speak French)https://pt-br.facebook.com (for Brazilians who speak Portuguese)https://pt-pt.facebook.com (for Portuguese people who speak Portuguese)
