This document describes metadata.json that's generated from PhoneNumberMetadata.xml by running npm run metadata:generate command. It serves as an intermediary step for generating all other metadata (such as metadata.min.json), and is therefore not included in the final distribution. See PhoneNumberMetadata.xml in Google's repo. They also have some docs on metadata fields too.
country_calling_codes — A list of countries by country calling code: some country calling codes are shared between several countries (for example, United States and Canada).
countries — Contains metadata for each country.
Country calling code, duplicated here for easy lookup of country calling code by country. Could be considered "reverse lookup" compared to country_calling_codes.
International Direct Dialing prefix when calling out of this country. "IDD prefixes" are used to call from one country to another. "IDD prefixes" originated when telephony was still analogue and analogue phones didn't have a + input. Nowadays, mobile phone users dial international numbers using a + rather than an "IDD prefix", but the mobile phone operating system replaces the + with an "IDD prefix" under the hood. For example, to call a Russian number +7 800 555 35 35 from US the dialled digits would be 01178005553535 where 011 is an "IDD prefix".
When a country supports different "IDD prefixes", the idd_prefix is a regular expression and default_idd_prefix is the default "IDD prefix".
Localized " ext. " prefix for this country. For example, in Russia it's " доб. ". Is only used for formatting phone numbers having "extensions" (usually these're organizational phone numbers: businesses, governmental institutions, educational institutions, etc).
When several countries share the same country calling code, these "leading digits" are the means of determining which one of these countries does a phone number belong to. For example, Antigua and Barbuda have leading_digits: "268" and share 1 country calling code with USA, so if an international phone number starts with +1268 then it belongs to Antigua and Barbuda.
leading_digits does not contain all the prefixes valid for a country: for example, 800 numbers are valid for all NANPA countries and are hence not listed here. leading_digits regular expression is used merely as a short-cut for working out which country a phone number comes from.
A regular expression covering all possible phone numbers for the country.
"National prefix", also known as "National Direct Dialing prefix". In the early days of analogue telephony, countries were divided into "areas" (for example, cities), and calling within an area (for example, a city) would only involve dialing a phone number without "area code" digits, but calling from one "area" (city) to another (city) would require dialing a "national prefix" first, so that the analogue telephone station would switch the user into "nation-wide" calling mode first.
For example, in New Zealand, the number that would be locally dialled as 09 345 3456 would be dialled from overseas as +64 9 345 3456. In this case, 0 is the national prefix.
Other national prefix examples: 1 in US, 0 in France and UK, 8 in Russia.
national_prefix_for_parsing is used to parse a national (significant) number from a phone number. Contrary to its name, national_prefix_for_parsing is used not just for parsing a "national prefix" out of a phone number (just national_prefix property would be sufficient for that) but for also parsing any other possible phone number prefixes out of a phone number, if there're any, and for any other cases like handling a missing 340 area code for US Virgin Islands. So it's actually not "national prefix for parsing" but rather "national number prefix for parsing".
For example, some countries (Argentina, Brazil) use "carrier codes", in which case national_prefix_for_parsing includes both national prefix and all possible "carrier codes". So, for example, to dial the number 2222-2222 in Fortaleza, Brazil (national prefix 0, area code 85) using the long distance carrier Oi (selection code 31), one would dial 0 31 85 2222 2222, and Brazil's national_prefix_for_parsing is 0(?:(1[245]|2[1-35]|31|4[13]|[56]5|99)(\d{10,11}))?.
As another example, some countries support "utility" prefixes, like Australia (national prefix 0) that supports 1831 prefix to hide your phone number when calling somebody (and 1832 to un-hide it when in "permanent" hiding mode), and so Australia's national_prefix_for_parsing is 0|(183[12]).
Another example are U.S. Virgin Islands (national prefix 1) whose phone numbers always start with a 340 area code because there's no other area code in this tiny (346.36 square kilometers) island country. So it's common for its citizens to call 693-4800 instead of (340) 693-4800, and Google's libphonenumber handles this case by national_prefix_for_parsing being 1|([2-9]\d{6})$.
Another type of "prefix" is a "carrier code". If national_prefix_transform_rule is defined and national_prefix_for_parsing has more than one "capturing group", then the first "capturing group" is the "carrier code". If national_prefix_transform_rule is not defined and national_prefix_for_parsing has any "capturing groups", then the first "capturing group" is the "carrier code".
If national_prefix_for_parsing regular expression contains "capturing groups" (parentheses), then national_prefix_transform_rule defines how a national phone number is parsed into a national (significant) number. So, in a way, they're the "two side of one coin", being "alter egos" of each other: whenever national_prefix_for_parsing removes a "significant" part of a phone number, it does so with a "capturing group", so that national_prefix_transform_rule would immediately put it back.
Using the above example for U.S. Virgin Islands, its national_prefix_for_parsing is 1|([2-9]\d{6})$, and national_prefix_transform_rule is 340$1, so a phone number 693-4800 would first be parsed by national_prefix_for_parsing into an empty string and $1 "captured group" being 6934800, and then that empty string would be transformed back into 3406934800 number by national_prefix_transform_rule, resulting into 693-4800 national phone number being parsed into 3406934800 national (significant) number.
Another case when national_prefix_formatting_rule is used is inside formats to define how national prefix changes how a phone number should be formatted.
Regular expressions for all possible phone number types for this country: fixed line, mobile, toll free, premium rate, etc.
A regular expression for a national (significant) number matching the type.
Possible lengths of a national (significant) number matching the type. Is always present.
Phone number examples for each of the phone number types.
Possible lengths of a national (significant) number for this numbering plan. This property is a combination of possible_lengths of all types. Is always present.
Describes all possible phone number formats for this country. May be missing if phone numbers aren't formatted for this country (there're many such countries, usually small islands).
A regular expression for a phone number supported by this format.
For example, in US there's only one possible phone number format, and it's pattern is (\d{3})(\d{3})(\d{4}), meaning that the national (significant) number must be 3 + 3 + 4 = 10 digits long (for example, 2133734253), and is divided into three groups of digits for formatting (in this case, 213, 373 and 4253).
Defines how the aforementioned groups of digits are combined when formatting a phone number.
For example, in US there's only one possible phone number format, and it's format is ($1) $2-$3, so 2133734253 national (significant) number is formatted as (213) 373-4253.
Parentheses arond "area code" only make sense when formatting a national phone number, so international phone numbers don't use them, hence the explicit international_format in addition to the national format.
For example, in US there's only one possible phone number format, and it's format is ($1) $2-$3, while its international_format is $1-$2-$3, meaning that 2133734253 national (significant) number is formatted as +1 213 373-4253 when formatted for international dialing.
national_prefix_formatting_rule is sometimes used to define how national prefix changes how a phone number should be formatted. For example, in Russia (national prefix 8), all formats have national_prefix_formatting_rule 8 ($1), meaning that a 88005553535 phone number is first stripped of 8 national prefix into a 8005553535 national (significant) number, then the national (significant) number is first parsed using (\d{3})(\d{3})(\d{2})(\d{2}) format pattern and then formatted using $1 $2-$3-$4 format format into 800 555-35-35, and, after that, national_prefix_formatting_rule 8 ($1) is applied, resulting in 8 (800) 555-35-35. Have the phone number been input without the 8 national prefix, the formatted phone number would be 800 555-35-35 (without parentheses).
This field specifies whether the national prefix can be omitted when formatting a number in national format, even though it usually wouldn't be. For example, a UK (GB) number would be formatted by libphonenumber as 020 XXXX XXXX. If they have commonly seen this number written by people without the leading 0, for example as (20) XXXX XXXX, libphonenumber would be updated with national_prefix_is_optional_when_formatting being true for that format of GB country.
"Leading digits" patterns are used in AsYouType formatter to choose a format suitable for the phone number being input: if a phone number's "leading digits" match those of a format, then that format is used to format the phone number being input. Each subsequent leading digits pattern in leading_digits_patterns array requires one more leading digit.
There're calling codes that don't correspond to any country. For example, "Global Mobile Satellite System" (+881). Such phone numbering systems are called "non-geographic entities" in Google's code. These "non-geographic entitites" reside in their own nonGeographic property, analogous to the countries property. nonGeographic is an object with keys being calling codes of the corresponding "non-geographic entities", and values being same as the values of the countries property.
"Non-geographic" numbering plans don't have possible_lengths.