# E.164

E.164 is the ITU-T standard that gives every phone number one unambiguous international form: a plus sign, a country calling code, and at most fifteen digits.

Date: 2026-09-10

E.164 is the ITU-T standard that gives every phone number one unambiguous international form: a plus sign, a country calling code, and at most fifteen digits in total, with no spaces, brackets or dashes. `+14155550142` is E.164; `(415) 555-0142` is the same number written for a person.

## What Spaw answers

`e164` is the canonical form and the field to store. Three others carry the same number written differently: `national` for display inside its own country, `international` for display across borders, and `rfc3966` as a `tel:` URI for a dial link.

## Why the country parameter exists

E.164 is unambiguous only when the calling code is present. A number typed without one — `4155550142`, or a national form beginning with a trunk `0` — could belong to several countries, so a lookup needs `country` to know which numbering plan to read it against. Without one the answer is [`missing_country`](/docs/reasons/missing_country), which is free.

An API key can carry a default country, applied only when the request body names none at all; an explicit `country: null` still means "read it from the calling code".

Reference: https://spaw.co/glossary/e164