# E.164

> E.164 is the international numbering format for phone numbers: a plus sign, the country code and the national number, up to 15 digits, with no spaces, zeros or punctuation.

E.164 is the ITU-T recommendation that defines how a telephone number is written internationally: `+`, country code (1 to 3 digits), then the subscriber number, for a maximum of 15 digits. `+14155550142` and `+447700900123` are E.164; `07700 900123` is not.

APIs use E.164 because it is unambiguous: the country, and therefore the route, the price and the sender rule, can be read from the prefix. Local formats need a default country to be interpreted, and the same digits can mean different numbers in different countries.

At SMSMeteor: the API accepts E.164 only and rejects anything else with `invalid_number` before billing; the panel importer converts local formats when you tell it the default country.

Related terms: [MSISDN](https://smsmeteor.com/glossary/msisdn), [REST API (SMS)](https://smsmeteor.com/glossary/rest-api), [Failed vs rejected](https://smsmeteor.com/glossary/failed-vs-rejected)

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Source: https://smsmeteor.com/glossary/e164 (HTML). Generated by SMSMeteor from the same data as the page. Summary of the whole site: https://smsmeteor.com/llms.txt