Twenty-six regional indicator symbols are used to build standard emoji country flags.
The symbols correspond to the letters A through Z. A flag emoji is generally represented by a pair of regional indicator symbols whose sequence matches a two-letter country or territory code. For example, the United States flag uses the regional indicators for U and S.
These symbols are not ordinary visible alphabetic letters. They are special Unicode characters designed to work together in flag sequences, and platforms render recognized pairs as a single flag image or glyph. Unsupported or unrecognized combinations may appear as separate letter-like symbols.
The system is linked to ISO 3166-1 alpha-2 codes, which is why many national flags use familiar two-letter abbreviations. The number of regional indicators remains 26 because it is based on the English alphabet.