ISO 3166 is the international standard maintained by ISO for country and subdivision codes. ISO 3166-1 covers current countries; ISO 3166-3 records former codes such as SU (USSR) or YU (Yugoslavia).

Alpha-2 (two letters, e.g. TW) is the most common form, used in domains and i18n locale prefixes. Alpha-3 (three letters, e.g. TWN) is more readable and used in passports and the Olympics.

Numeric uses three digits (e.g. 158) and is language-independent, so it works regardless of script. It is common in UN datasets and multi-language data integration.

Taiwan's ISO 3166-1 codes are TW (alpha-2), TWN (alpha-3), and 158 (numeric). The ISO official name is "Taiwan, Province of China", but most localized contexts simply call it Taiwan.

After 1991 SU was retired from ISO 3166-1 and moved to ISO 3166-3 as a "withdrawn" code, with 15 successor states (RU, UA, BY, KZ, UZ, TJ, KG, TM, AM, AZ, GE, MD, LT, LV, EE) each getting their own alpha-2.

Filling cross-border forms (country dropdown), integrating multi-country databases (unifying country column schema), writing i18n / l10n locale prefixes, or researching historical code transitions.

When a country renames itself or its government changes (e.g. Burma → Myanmar), ISO typically keeps the original numeric code for continuity in UN statistics. The old alpha-2/alpha-3 retires to ISO 3166-3 while the new code inherits the numeric.

This tool covers only ISO 3166-1 (country codes) and ISO 3166-3 (former country codes). ISO 3166-2 has 5,000+ subdivision codes worldwide and is out of scope; consult the official ISO Online Browsing Platform for that.

All three have their own alpha-2 codes (TW, HK, MO) in ISO 3166-1. The official ISO names include qualifiers — "Taiwan, Province of China", "Hong Kong" and "Macao" (both listed as Special Administrative Regions). They are treated as separate entries for coding purposes, regardless of the political naming.