Emoji tag sequences for regional flags are derived from ISO 3166-2.
ISO 3166-2 is the part of the ISO 3166 standard that identifies subdivisions of countries, such as states, provinces, counties, and territories. Unicode emoji tag sequences use the relevant subdivision letters after a black flag base, allowing sequences for regional flags such as England, Scotland, and Wales.
This system differs from the one used for national flags. National flags normally use two regional indicator symbols based on ISO 3166-1 alpha-2 country codes—for example, GB for the United Kingdom. Regional tag sequences instead represent subdivision codes such as ENG, SCT, and WLS, with formatting tag characters carrying the letters.
The existence of a valid ISO 3166-2 code does not guarantee broad emoji support. Unicode has historically recommended only a limited number of subdivision-flag sequences for general interchange, and platforms may display unsupported sequences as a plain black flag or separate invisible-tag behavior. ISO 3166-2 is therefore the source standard, while Unicode defines how the sequence is encoded and displayed.