# Phone Number Key: `identity.person.phone_number` Telephone number in various formats. Locale-specific due to digit grouping, area code positions, and formatting conventions (e.g., US +1 (xxx) xxx-xxxx vs EU +xx-xxx-xxx-xxxx). May include country code, area code, and extension. Page: Samples: `+1 (555) 123-4567`, `555-123-4567`, `+44 20 7946 0958`, `+33 1 42 68 53 00`, `07911 123456` ## Background ### Origin The numbering plan behind phone numbers worldwide is ITU-T Recommendation E.164, titled The international public telecommunication numbering plan.[[1]](https://www.itu.int/rec/T-REC-E.164) The first issue of E.164 was published in 1988 in Blue Book Fascicle II.2.[[2]](https://en.wikipedia.org/wiki/E.164) E.164 numbers are limited to digits only, with a maximum of fifteen digits.[[2]](https://en.wikipedia.org/wiki/E.164) E.164 divides the digit string into a country code of one to three digits, followed by the subscriber number.[[2]](https://en.wikipedia.org/wiki/E.164) How a number is written down is a separate ITU-T Recommendation, E.123, titled Notation for national and international telephone numbers, e-mail addresses and web addresses.[[3]](https://www.itu.int/rec/T-REC-E.123) The edition of E.123 in force is dated February 2001, and it superseded an edition of November 1988.[[3]](https://www.itu.int/rec/T-REC-E.123) E.123 defines the plus sign as the international prefix symbol, written before the country code.[[4]](https://en.wikipedia.org/wiki/E.123) In international notation, E.123 says only spaces should be used to separate groups of digits.[[4]](https://en.wikipedia.org/wiki/E.123) E.123 uses parentheses in national notation to mark digits that are sometimes not dialled, such as an area code.[[4]](https://en.wikipedia.org/wiki/E.123) Parentheses are not allowed in E.123's international notation.[[4]](https://en.wikipedia.org/wiki/E.123) ### Use RFC 3966, which defines the tel URI, allows phone numbers to contain visual separators.[[5]](https://www.rfc-editor.org/rfc/rfc3966) RFC 3966 says visual separators merely aid readability and are not used for URI comparison or placing a call.[[5]](https://www.rfc-editor.org/rfc/rfc3966) In RFC 3966, globally unique numbers are identified by the leading + character.[[5]](https://www.rfc-editor.org/rfc/rfc3966) RFC 3966 identifies phone extensions with an extension parameter.[[5]](https://www.rfc-editor.org/rfc/rfc3966) Strip the separators and keep the digits, the leading plus and any extension apart before comparing or deduplicating numbers. (Meridian's view) A number without a country code cannot be made international safely unless you know which country the record belongs to, so carry that context alongside the column. (Meridian's view) Google's libphonenumber is a common Java, C++ and JavaScript library for parsing, formatting and validating international phone numbers.[[6]](https://github.com/google/libphonenumber) libphonenumber formats the Swiss number 044 668 18 00 as +41 44 668 18 00 in international form and +41446681800 in E.164 form.[[6]](https://github.com/google/libphonenumber) libphonenumber's isPossibleNumber check uses only length information, while isValidNumber uses length and prefix information for a region.[[6]](https://github.com/google/libphonenumber) A pattern match only shows that a value looks like a phone number; use a library with per-country rules when you need to know whether it could be a real one. (Meridian's view) In the North American Numbering Plan, only 555-0100 through 555-0199 are now specifically reserved for fictional use.[[7]](https://en.wikipedia.org/wiki/555_%28North_American_Numbering_Plan%29) ### Where you'll meet it OpenStreetMap asks for phone numbers in international (ITU-T E.164) format, written with a plus sign, country code, area code and local number.[[8]](https://wiki.openstreetmap.org/wiki/Key:phone) OpenStreetMap separates multiple phone numbers in one phone tag with a semicolon.[[8]](https://wiki.openstreetmap.org/wiki/Key:phone) ## Sources 1. [E.164 : The international public telecommunication numbering plan](https://www.itu.int/rec/T-REC-E.164) — catalogue entry 2. [E.164](https://en.wikipedia.org/wiki/E.164) — secondary source 3. [E.123 : Notation for national and international telephone numbers, e-mail addresses and web addresses](https://www.itu.int/rec/T-REC-E.123) — catalogue entry 4. [E.123](https://en.wikipedia.org/wiki/E.123) — secondary source 5. [RFC 3966: The tel URI for Telephone Numbers](https://www.rfc-editor.org/rfc/rfc3966) — standard 6. [google/libphonenumber](https://github.com/google/libphonenumber) — documentation 7. [555 (North American Numbering Plan)](https://en.wikipedia.org/wiki/555_%28North_American_Numbering_Plan%29) — secondary source 8. [Key:phone](https://wiki.openstreetmap.org/wiki/Key:phone) — organisation