Guide to Country Codes (ISO 3166 and Dialing Codes)

Why this matters

A logistics platform onboards a new market. The form needs ISO-3166 alpha-2 codes (KR), the phone validator needs the +calling code (+82), the currency dropdown wants KRW, and the analytics dashboard reports by alpha-3 (KOR). All four come from different IANA / ISO / ITU lists. A single reference that joins them prevents bugs (Slovenia is SI not SL, Switzerland is CH not SW) and saves time.

Three real scenarios

Backend Developer

Validate phone numbers globally

Look up the calling code, drop the dial-prefix into the formatter library.

Reliable signup form

Data Analyst

Join a CSV with two-letter codes to one with three-letter codes

Use the cross-reference to convert alpha-2 → alpha-3 in bulk.

Correct join key

Marketing Operations

Localize a landing page with the right TLD and currency

Look up .co.uk vs .uk, GBP, and "United Kingdom" canonical name.

On-brand regional site

Walkthrough — using the reference

Open the Country code reference.

Search by name or code
"Korea" surfaces both DPRK (KP) and ROK (KR); type the alpha-2 to disambiguate.
Read the country card
Alpha-2, alpha-3, numeric, calling code, capital, currency code, primary TLD, official languages.
Browse by region
Asia, Europe, Africa, Americas, Oceania — useful when you need to enumerate a region.
Look up a single code in detail
Click a country to see additional metadata (sub-region, ISO short name, alternate names).
Copy in the format you need
JSON, CSV, or a single field for spreadsheets and code.

A typical lookup card

"Switzerland"

Card

Country:        Switzerland
Alpha-2:        CH
Alpha-3:        CHE
Numeric:        756
Calling code:   +41
Capital:        Bern
Currency:       CHF — Swiss Franc
TLD:            .ch
Languages:      de, fr, it, rm

Power tips

Use alpha-2 in URLs (e.g. /locale/jp); it's the established convention. Use alpha-3 in BI dashboards where ambiguity hurts.
Calling codes can be shared (Russia and Kazakhstan both +7). Disambiguate by area code prefix in your validator.
TLDs are not always one per country. UK has .uk and .co.uk; Brazil has .br and .com.br. The reference shows the primary; consult ICANN for the full delegation.
Some codes change over time. Czechia: CZ (alpha-2) is stable; the ISO short name changed from "Czech Republic" to "Czechia" in 2016.

Common pitfalls

Common mistake

Confusing alpha-2 with linguistic codes

ISO-639 (language) and ISO-3166 (country) overlap (e.g. de is German and DE is Germany). They're different lists; don't use one when you need the other.

Common mistake

Codes for de-facto vs de-jure entities

Kosovo, Taiwan, Western Sahara have contested status. ISO uses provisional codes (XK, TW, EH). Some payment processors don't accept them; check before launching.

Common mistake

Currency code mismatch with the country

Eurozone countries all share EUR. Several countries officially use the US dollar (USD) without minting their own. Don't infer currency from the country alone.

When this is the wrong tool

Sub-national codes (states, provinces, ISO-3166-2) require a more granular dataset. Consider GeoNames or the date-holidays tool's underlying database.
Real-time exchange rates — pair with an FX API; this reference shows currency codes, not rates.
Phone number validation logic — libphonenumber (Google) is the canonical library; this reference is for the dial-prefix mapping.

FAQ

ISO-3166 reserves codes for transitional or sub-territorial entities (e.g., EU for the European Union, XX for unknown). These are valid in some contexts but not as country identifiers.

What's the difference between numeric and alpha codes?

Numeric codes (756 for Switzerland) are language-neutral and immune to romanization differences. Useful in international banking (SWIFT/BIC), where alpha codes can be ambiguous across scripts.

Is the data offline?

Yes. The data is bundled with the page; the lookup never makes a network request beyond the initial page load.

Next steps

Pair country lookups with holiday awareness using the Today Holiday tool.
Check time zones for the chosen country with the World Clock.
Compare working windows across markets with the Time Zone Comparator.

Why this matters

Three real scenarios

Backend Developer

Validate phone numbers globally

Look up the calling code, drop the dial-prefix into the formatter library.

Reliable signup form

Data Analyst

Join a CSV with two-letter codes to one with three-letter codes

Use the cross-reference to convert alpha-2 → alpha-3 in bulk.

Correct join key

Marketing Operations

Localize a landing page with the right TLD and currency

Look up .co.uk vs .uk, GBP, and "United Kingdom" canonical name.

On-brand regional site

Walkthrough — using the reference

Open the Country code reference.

Search by name or code
"Korea" surfaces both DPRK (KP) and ROK (KR); type the alpha-2 to disambiguate.
Read the country card
Alpha-2, alpha-3, numeric, calling code, capital, currency code, primary TLD, official languages.
Browse by region
Asia, Europe, Africa, Americas, Oceania — useful when you need to enumerate a region.
Look up a single code in detail
Click a country to see additional metadata (sub-region, ISO short name, alternate names).
Copy in the format you need
JSON, CSV, or a single field for spreadsheets and code.

A typical lookup card

"Switzerland"

Card

Country:        Switzerland
Alpha-2:        CH
Alpha-3:        CHE
Numeric:        756
Calling code:   +41
Capital:        Bern
Currency:       CHF — Swiss Franc
TLD:            .ch
Languages:      de, fr, it, rm

Power tips

Use alpha-2 in URLs (e.g. /locale/jp); it's the established convention. Use alpha-3 in BI dashboards where ambiguity hurts.
Calling codes can be shared (Russia and Kazakhstan both +7). Disambiguate by area code prefix in your validator.
TLDs are not always one per country. UK has .uk and .co.uk; Brazil has .br and .com.br. The reference shows the primary; consult ICANN for the full delegation.
Some codes change over time. Czechia: CZ (alpha-2) is stable; the ISO short name changed from "Czech Republic" to "Czechia" in 2016.

Common pitfalls

Common mistake

Confusing alpha-2 with linguistic codes

ISO-639 (language) and ISO-3166 (country) overlap (e.g. de is German and DE is Germany). They're different lists; don't use one when you need the other.

Common mistake

Codes for de-facto vs de-jure entities

Kosovo, Taiwan, Western Sahara have contested status. ISO uses provisional codes (XK, TW, EH). Some payment processors don't accept them; check before launching.

Common mistake

Currency code mismatch with the country

Eurozone countries all share EUR. Several countries officially use the US dollar (USD) without minting their own. Don't infer currency from the country alone.

When this is the wrong tool

Sub-national codes (states, provinces, ISO-3166-2) require a more granular dataset. Consider GeoNames or the date-holidays tool's underlying database.
Real-time exchange rates — pair with an FX API; this reference shows currency codes, not rates.
Phone number validation logic — libphonenumber (Google) is the canonical library; this reference is for the dial-prefix mapping.

FAQ

ISO-3166 reserves codes for transitional or sub-territorial entities (e.g., EU for the European Union, XX for unknown). These are valid in some contexts but not as country identifiers.

What's the difference between numeric and alpha codes?

Numeric codes (756 for Switzerland) are language-neutral and immune to romanization differences. Useful in international banking (SWIFT/BIC), where alpha codes can be ambiguous across scripts.

Is the data offline?

Yes. The data is bundled with the page; the lookup never makes a network request beyond the initial page load.

Next steps

Pair country lookups with holiday awareness using the Today Holiday tool.
Check time zones for the chosen country with the World Clock.
Compare working windows across markets with the Time Zone Comparator.