This is an example of the primary language subtag for Spanish, subtag must always be preceded by a specific primary language subtag, there can only be one in a language tag, and it comes before any other subtags.
Examples of language tags including extlang subtags are: Language extlang combinations are provided to accommodate legacy language tag forms, however, there is a single language subtag available for every language extlang combination.
XHTML/HTML coders (using editors or scripting), script developers (PHP, JSP, etc.), schema developers (DTDs, XML Schema, Relax NG, etc.), XSLT developers, Web project managers, standards implementers, and anyone who needs an overview of how language tags are constructed using BCP47. Unfortunately, it is not possible to tell, when reading RFC 1766 or RFC 3066 that these specifications have been obsoleted and replaced by other specifications.attribute for XML In both cases, language information is inherited by elements inside the one where the declaration was made, unless one of those elements declares a different language (in the same way). Most language tags consist of a two- or three-letter language subtag.For example, language tags are lower case, alphabetic region subtags are upper case, and script tags begin with an initial capital. When you use these subtags you are free to do as you like, unless you are constrained by the rules of the system you are working with.For HTML and XML language markup, the case should not matter.The subtags come from, and are kept up to date with, the list of ISO 15924 script codes.
Only one script subtag can appear in a language tag, and it must immediately follow the language or any extlang subtag. You should only use script tags if they are necessary to make a distinction you need.That language subtag should be used rather than the language extlang combination, where possible.For example, use Macrolanguages The primary language subtags used with an extlang subtag are known as macrolanguages, and encompass a number of languages with more specific primary language subtags.For example, you could use Although for common uses of language tags it is not likely that you will need to specify the script, there are one or two situations that have been crying out for it for some time. There are many Chinese dialects, often mutually unintelligible, but these dialects are all written using either Simplified or Traditional Chinese script.People typically want to label Chinese text as either Simplified or Traditional, but until recently there was no way to do so.If you have been using RFC 1766, RFC 3066, or RFC 4646 you do not need to make any changes to your tags.