BCP-47

BCP-47 is the Best Current Practices for language tags. Such tags allow to identify spoken and written languages.

Basic structure of language tags:

• ASCII subtags
• Up to eight characters long (?)
• Separated by hyphens
• Case-independent (zh = ZH = Zh = zH)

The hyphens separate each element from one another. The first element is required, up to three additional elements are optional.

These elements are:

• Language
• Script
• Region
• Variant

Some examples of language tags are:

• en-US (English, United States)
• de-DE (German, Germany)
• de-CH (German, Switzerland)
• it-CH (Italian, Switzerland)
• zh-Hant (Chinese, traditional script)
• zh-Hans (Chinese, simplified script)
• zh-Hans-HK (Chinese, simplified script, Hong Kong)

A language might be tagged und (undetermined?), for example und-Latn. This matches any language that uses Latin script.