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 defined for every country and 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).
National (significant) number "leading digits" pattern. It's only defined for about 20% of the countries, and in most cases it's for resolving ambiguity in cases when there're groups of countries sharing the same "country calling code". Although, if there's a group of countries sharing the same "country calling code", it doesn't necessarily mean that those countries have a leading_digits pattern defined.
For example, USA and Canada share the same 1 country calling code, but neither of them have a leading_digits pattern defined. On the other hand, Antigua and Barbuda also shares the same 1 country calling code, and its leading_digits pattern is "268", so if an international phone number starts with +1268 then it's certain that it belongs to Antigua and Barbuda, so "leading digits" are, in some cases, a quick way of determining which one of the countries sharing the same country calling code does a phone number belong to.
While in most cases a leading_digits pattern is a sequence of digits like "268" for Antigua and Barbuda, in other cases it's a pattern like "8001|8[024]9" for Dominican Republic.
Overall, leading_digits patterns are only used as a performance speed-up trick when determining which country a phone number belongs to: the check is still simpler than looking for a match against all of the precise phone number digit patterns of every country sharing a given country calling code.
For that reason, matching a leading_digits pattern is a sufficient but not a necessary condition for a phone number to belong to a country: if a leading_digits pattern exists and a phone number matches it that it's certain that the phone number belongs to the country, and no other country. But, if there's no leading_digits pattern, or if the phone number doesn't match the leading_digits pattern, then it doesn't mean that the phone number doesn't belong to the country.
For example, "toll free" numbers starting with 800 are valid for all countries having 1 country calling code, so it doesn't make sense to include 800 in their leading_digits patterns. But one could say that those "toll free" numbers could be thought of as an unrelated edge case that can be ignored if the application only deals with human phone numbers.
Another example of phone number that're not included in leading_digits patters are "personal" (satellite) numbers that start with 5xx for +1 calling code.
The last example are mobile phone numbers which sometimes have identical patterns across the countries sharing the same "country calling code". An example are Finland (FI) and Åland Islands (AX) which share the same +358 calling code and the same pattern for mobile phone numbers. And while +358 457 XXX XXXX mobile numbers could belong both to Finland or Åland Islands, Åland Islands' leading_digits pattern is just 18 which doesn't include any mobile numbers at all.
So leading_digits patterns could only be used for a quick "positive" check and they can't be used for ruling out any countries.
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 also for parsing any other possible phone number prefixes out of a phone number, if there're any, and for any other cases like fixing a missing area code. So it's actually not a "national prefix for parsing", but rather a "national (significant) number extraction mechanism".
national_prefix_for_parsing is a regular expression that could (or could not) have some "capturing groups". If there're any "capturing groups", then national_prefix_for_parsing is accompanied by national_prefix_transform_rule: yet another incorrect name by Google, because national_prefix_transform_rule is not a "rule for transforming a national prefix", but rather a "template to transform the captured groups into a national (significant) number".
There're different types of possible "prefixes" a phone number could have. One example are "carrier codes". If a national_prefix_transform_rule is defined and the national_prefix_for_parsing has more than one "capturing group", then the second "capturing group" is a "carrier code". If a national_prefix_transform_rule is not defined and the national_prefix_for_parsing has at least one "capturing group", then the first "capturing group" is a "carrier code".
For example, countries like Argentina and Brazil do use "carrier codes", and their national_prefix_for_parsing regular expressions include 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, for parsing such numbers, Brazil's national_prefix_for_parsing is 0(?:(1[245]|2[1-35]|31|4[13]|[56]5|99)(\d{10,11}))?, which matches the whole 0318522222222 number with captured group #1 being 31 ("carrier code") and captured group #2 being 8522222222 (which is also the actual national (significant) number, because national_prefix_transform_rule is $2).
Another example of a "prefix": some countries support "utility" prefixes, like Australia (national prefix 0) that supports 1831 prefix to hide your phone number when calling somebody (and 1832 to un-hide it when in "permanent" hiding mode), and so Australia's national_prefix_for_parsing is 0|(183[12]), which matches the 1831 prefix as group #1.
Another example of using a national_prefix_for_parsing / national_prefix_transform_rule pair, in this case for reasons completely unrelated to any "prefixes", are U.S. Virgin Islands (national prefix 1) whose phone numbers always start with a 340 area code because there's no other area code in this tiny (346.36 square kilometers) island country. So it's common for its citizens to call 693-4800 instead of (340) 693-4800, and Google's libphonenumber handles this case by national_prefix_for_parsing being 1|([2-9]\d{6})$, which matches 6934800 number as group #1, which is later used in national_prefix_transform_rule, which is 340$1, meaning that it prepends 340 to the group #1 being the 6934800 number, resulting in 3406934800 national (significant) number.
If national_prefix_for_parsing matches any "capturing groups", then it doesn't provide the actual national prefix being extracted, or even guarantee the fact that there is a national prefix: in those cases, it just converts a national number to a national (significant) number by applying a national_prefix_for_parsing/national_prefix_transform_rule transform to it.
For example, in AG country, phone numbers are same as in the US, with the only difference that they start with 268. The national_prefix_for_parsing is 1|([457]\\d{6})$. If a number is entered with a leading 1 ("1 268 464 1234"), then there're no "capturing groups" in that regular expression, so the national prefix is the entire substring matched by the regular expression: "1". If a number is entered without a leading 1 ("268 464 1234"), then the regular expression doesn't match, and the number doesn't have a national prefix (which is true). If a number is entered without the "area code" 268 (just "464 1234"), then national_prefix_for_parsing regular expression matches with the "capturing group" being "4641234", and then national_prefix_transform_rule 268$1 transforms that "capturing group" into a 2684641234 national (significant) number; and even though national_prefix_for_parsing did match, the phone number didn't have any national prefix.
Another example is Mexico (MX) that has no national_prefix_transform_rule and has national_prefix_for_parsing 0(?:[12]|4[45])|1: the ?: defines a "non-capturing group", so national_prefix_for_parsing has no "capturing groups", and, therefore, matches the actual national prefix of a phone number; that national prefix isn't used anywhere though: it's simply discarded, because all formats of Mexico have national_prefix_is_optional_when_formatting: true, meaning that a national prefix isn't used when formatting a phone number using any of those formats.
If no national_prefix_for_parsing has been defined, but national_prefix has been defined, then national_prefix_for_parsing is equal to national_prefix.
Whatever national prefix has been extracted, it's not used anywhere: instead, national_prefix_formatting_rule of a format already has a national prefix "hardcoded". For example, in Russia, national_prefix is 8, and national_prefix_formatting_rule of all formats is 8 ($1). So the code doesn't store the extracted national prefix anywhere: only the fact that the national prefix has been extracted is used to decide whether to apply national_prefix_formatting_rule when formatting the parsed number.
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 format.pattern (\d{3})(\d{3})(\d{2})(\d{2}) and then formatted using format.format $1 $2-$3-$4 while also replacing $1 in that format.format with format.national_prefix_formatting_rule which is 8 ($1), so the resulting format.format becomes 8 ($1) $2-$3-$4, and so the formatted number is 8 (800) 555-35-35. Have the phone number been input without the 8 national prefix, the national_prefix_formatting_rule wouldn't be applied, and format.format would stay $1 $2-$3-$4, and the formatted phone number would be 800 555-35-35.
In some cases (for example, in Argentina), format.format may exclude $1, so in those cases national_prefix_formatting_rule being 0$1 would actually mean 0$2, because there's no $1 "capturing group" in format.format, but there is $2 "capturing group" there.
This field specifies whether the national prefix can be omitted when formatting a number in national format. For example, a UK (GB) number would be formatted by libphonenumber as 020 XXXX XXXX. Have they seen this number commonly being written without the leading 0 (like (20) XXXX XXXX), they would have updated the metadata with national_prefix_is_optional_when_formatting being true for that format, so that such number, when formatted, wouldn't have national_prefix_formatting_rule applied to it. Otherwise, if national_prefix_is_optional_when_formatting is not set to true, national_prefix_formatting_rule is always applied (when present).
Specifies how a carrier code ($CC) together with the first group ($FG) in a national significant number should be formatted, if carrier codes are used when formatting the number for dialing. For example, if a format's format is $1 $2-$3 and domestic_carrier_code_formatting_rule is $NP $CC ($FG), then a national number, when having a carrier code, is formatted as national-prefix carrier-code ($1) $2-$3.
For example, Google's libphonenumber has formatNumberForMobileDialing() function that returns a number formatted in such a way that it can be dialed from a mobile phone within a specific country, and it adds "carrier codes" when dialing within certain countries (Brazil — when dialing from a mobile phone to any number, Colombia — when dialing from a mobile phone to a fixed line number). Since libphonenumber-js is not a dialing library, it doesn't provide such a function and doesn't use "carrier codes" when formatting phone numbers, so this property is ignored in this library.
"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.