E.164 phone number format

E.164 is the international standard format for telephone numbers: a plus sign, the country code, then the national number, with no spaces or punctuation, and at most 15 digits in total. +447700900001 is a UK mobile number written in E.164. The format is defined in ITU-T Recommendation E.164, published by the International Telecommunication Union.

#What does an E.164 number consist of?

It has three parts:

The maximum length is 15 digits, excluding the +. Country codes can be shared. +1 covers the United States, Canada and a number of Caribbean countries (the North American Numbering Plan), and +7 covers Russia and Kazakhstan. The country code alone doesn't always identify the country. The first digits of the national number are needed too.

#Why do APIs use E.164?

A number can be written in dozens of ways: 07700 900001, +44 (0)7700 900001, 0044 7700-900001. They all mean the same line. Converting everything to one canonical form is the only reliable way to:

• deduplicate a list, so the same person isn't checked or messaged twice;
• cache results per number;
• price and route per country;
• match numbers across systems (CRM, messaging provider, fraud tools).

MobileValidate converts every number to E.164 before deduplication, caching, pricing or any check. The e164 field in each result shows the converted form, and number_status shows whether the input was valid, invalid or a duplicate.

#How do you convert a national number to E.164?

1. Remove spaces, dashes, dots and brackets.
2. Remove the national trunk prefix (usually a leading 0; in North America a leading 1 dialled domestically).
3. Add + and the country code.

So 07700 900001 in the UK becomes +447700900001, and (202) 555-0143 in the US becomes +12025550143. Because step 3 needs the country, national-format input needs a country hint. In the API that is the default_country field (ISO code, for example "GB"). Well-maintained libraries such as Google's libphonenumber also check length and number ranges per country, which catches many typos before any check is paid for.

#Is a valid E.164 number a working number?

No. E.164 describes the format and whether the number fits the country's numbering plan. It says nothing about whether the number is assigned, reachable or in use on a messaging app. The number reachability entry explains the difference. To learn more, use a carrier lookup for line type and network, and channel checks such as the WhatsApp check.

#Which numbers are safe to use in examples?

Use ranges reserved for fiction. In the UK, Ofcom reserves 07700 900000 to 07700 900999 for drama and they are never assigned to subscribers. MobileValidate's test mode uses numbers from this range, such as +447700900001.