Taiwan ISO Codes: TW, TWN, and 158

Need Taiwan’s country code for a form, database, or website? The correct ISO code depends on the format requested: Taiwan’s two-letter code is TW, its three-letter code is TWN, and its numeric code is 158. These are not interchangeable with Taiwan’s internet domain, telephone calling code, currency code, or Olympic identifier. This guide explains how to choose the right one and avoid entering a code from the wrong system.

Taiwan ISO Codes at a Glance

ISO 3166-1 provides country identifiers in two-letter, three-letter, and numeric formats. Use the format specified by the field or system you are completing. A form may validate both the code and its length, so the right letters in the wrong format can still be rejected. If a country selector is available, selecting Taiwan by name can also help avoid confusion between standards.

The Two-Letter Country Code: TW

TW is Taiwan’s ISO 3166-1 alpha-2 code. It is the Taiwan two-letter country code to enter when a form, database, or API specifically asks for an ISO alpha-2 value. The IANA time zone database’s country-code table lists TW for Taiwan.

Enter the two letters as shown, without adding a period or other prefix. Although TW is a common country abbreviation, it is not a universal answer for every system. A service may use its own country list or ask for a different identifier. Follow the field label and instructions rather than assuming that every two-letter code field uses ISO 3166-1.

The Three-Letter Code: TWN

TWN is Taiwan’s ISO 3166-1 alpha-3 code. Use it when a system specifically requests a three-letter ISO country code. For example, Precisely’s geocoding documentation identifies TWN as the ISO alpha-3 code for Taiwan.

TWN and TW identify the same place in different ISO formats, but they are not interchangeable in a field that validates one format. Check whether the field asks for alpha-2 or alpha-3 before entering a value; adding a third letter to a two-letter field, or shortening a three-letter value, may cause a validation error. Also, not every three-letter identifier used by an organization is an ISO alpha-3 code.

The Numeric ISO Code: 158

158 is Taiwan’s ISO 3166-1 numeric code. It is distinct from both TW and TWN. Enter 158 only when a data field requests the numeric ISO country code; do not substitute it for an alphabetic code or treat it as a telephone prefix.

The numeric value is written as 158, not as a number to calculate or convert. If a system requests a numeric country code, enter the value in the format it specifies; if it asks for letters, use the corresponding alphabetic code instead. The fact that the numeric identifier has three digits does not make it equivalent to the three-letter code TWN.

Taiwan’s ISO Codes and Other Identifiers

Several short codes are associated with Taiwan, but each belongs to a particular system. The purpose of the field—not just the number of letters or digits—determines which one to use. Similar-looking abbreviations can refer to a domain, a phone connection, a currency, or an organization’s own classification rather than an ISO country code.

ISO Country Codes Are Not Calling or Currency Codes

ISO 3166-1 codes identify a country or territory in country-code fields. Telephone numbering and currency identification use different standards and serve different purposes.

+886 is Taiwan’s international calling code. TWD is the currency code for the New Taiwan dollar. Neither is an ISO 3166-1 country code, and neither can replace TW, TWN, or 158 in an ISO country field. In the same way, TW is not a phone prefix or a currency code.

For example, a country field asking for an ISO two-letter value calls for TW, while a telephone field asking for an international calling code calls for +886. A currency field uses TWD to identify the currency, rather than the country. These values answer different questions, even when they appear together in a form or dataset.

Taiwan’s Internet Domain: .tw

.tw is Taiwan’s country-code top-level domain, used as an internet domain ending. It is closely associated with the ISO alpha-2 letters TW, but it is a domain suffix, not another format of the ISO country code. The IANA root-zone record lists .tw as a country-code top-level domain.

Use .tw when referring to a domain name, and use TW when a form requests the ISO alpha-2 code. The dot is part of the domain suffix, not part of the ISO code. A web address ending in .tw therefore does not mean that .tw should be entered into a country-code field.

Why the Olympic Code TPE Is Different

Olympic listings use TPE for Chinese Taipei, rather than Taiwan’s ISO alpha-3 code, TWN. The IOC country code list identifies TPE in this Olympic context.

This difference reflects the fact that codes belong to particular standards and organizations. TPE is appropriate when an Olympic system requests its Olympic code; it does not replace TWN in an ISO alpha-3 field. If a form uses a different organization’s terminology, rely on that form’s stated code system rather than assuming Olympic and ISO identifiers match.

Which Taiwan Code Should You Use?

Choose the identifier that matches the field’s stated system and format. A short value is not necessarily an ISO code simply because it resembles one. If instructions say only “country code,” look for an example, a format description, or a country selector to determine what the receiving system expects.

Match the Code to the Field or Standard

For an ISO 3166-1 field, use TW for alpha-2, TWN for alpha-3, or 158 for numeric. For other purposes, use .tw as the domain suffix, +886 as the calling code, and TWD as the currency code. Use TPE only when the Olympic identifier is requested.

Before submitting a value, compare it with the requested format: two letters, three letters, or digits. Don’t add a country name, punctuation, or a different system’s prefix unless the field specifically asks for it. If you are entering a value in a form, database, or API, check its instructions for the required code system and format. This is especially useful when a field says only “country code,” because that label may not specify whether it expects two letters, three letters, digits, or an organization-specific identifier.

Conclusion: Taiwan’s Current ISO Codes

Taiwan’s ISO 3166-1 codes are TW (alpha-2), TWN (alpha-3), and 158 (numeric). Use the one that matches the requested ISO format, and keep it distinct from .tw, +886, TWD, and the Olympic code TPE.