The ISO 639-1 code for the German language is de.
ISO 639-1 assigns standardized two-letter codes to individual languages for use in catalogs, websites, libraries, software, and international data exchange. The code is written in lowercase, so “de” is the standard form rather than “DE” or “ger.”
The code reflects German’s native name, Deutsch, which explains why it does not resemble the English word “German.” This is a common source of confusion, especially because German also has the ISO 639-2 codes “deu” and “ger,” both associated with the language in three-letter coding systems.
The code “de” should also not be confused with Germany’s internet country-code domain, .de. Both are connected historically to Deutschland or Deutsch, but they belong to different standards: ISO 639-1 identifies languages, while country-code domains identify internet territories.