E.164 Numbers: How They Work and Why They Matter

E.164 numbers are a standard way to identify phone numbers globally. They're a unique series of digits that help phones and computers understand where to send calls and messages.

E.164 numbers are made up of a country code followed by a national destination code and a subscriber number. This structure is crucial for international communication.

These numbers are used to route calls and messages between different countries and networks. The country code is a two-digit number that identifies the country where the number is registered.

E.164 numbers have become essential for international communication, enabling people to connect with others across the globe.

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E.164 is a standard format for international telephone numbers recommended by the International Telecommunication Union.

This format ensures that each PSTN device has a distinct and unique number worldwide.

A globally unique telephone number will ensure that calls and SMS can be routed correctly to different individual phones worldwide.

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E.163 was the former ITU-T recommendation for describing telephone numbers for the public switched telephone network (PSTN).

In the United States, this was formerly referred to as a directory number.

E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.

E.164 is a recommendation that contains specific criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code 991.

This three-digit code is assigned for the purpose of conducting an international non-commercial trial, giving the applicant a unique identifier for testing purposes only.

The E.164 country code 991 is shared among applicants, which is why a three-digit identification code is necessary to distinguish between them.

This temporary assignment is specifically designed for non-commercial trials, implying that the code is not meant for commercial use or long-term applications.

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The E.164 format is a standard for international telephone numbers recommended by the International Telecommunication Union.

This format ensures that each Public Switched Telephone Network (PSTN) device has a distinct and unique number worldwide.

A globally unique telephone number is essential for correctly routing calls and SMS to different individual phones worldwide.

The E.164 format guarantees that each PSTN device has a one-of-a-kind number that can be recognized globally.

With a unique number, you can rest assured that your calls and messages will reach their intended destination, no matter where you are in the world.

By using the E.164 format, you can avoid misunderstandings and misdeliveries that can happen with non-standard or duplicate numbers.

The E.164 recommendation provides the telephone number structure and functionality for five categories of telephone numbers used in international public telecommunications. Each category has its own components and digit analysis requirements for successful routing of calls.

The numbering structure is based on a fifteen-digit numbering space, which was increased from twelve digits in 1997. This change allowed for more flexibility and expansion of the numbering system.

Here is a breakdown of the E.164 number components:ComponentDescriptionCountry Code

3 digits

Identification Code

1 to 4 digits

Subscriber Number

maximum 12 digits − number of digits in the identification code

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The Country Code is the first part of the E.164 number, representing the international country calling code. The Identification Code is the second part, which can range from 1 to 4 digits. The Subscriber Number is the final part, which can have a maximum of 12 digits, minus the number of digits in the Identification Code.

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E.164 is a standard for international telephone numbering, and it's used to identify countries and their respective phone number formats. It's like a map for phone numbers.

E.164 numbers are made up of a country code, which is a unique identifier for each country. The country code for the United States, for example, is +1.

Each country's phone number format is determined by its country code. In the United States, phone numbers are typically 10 digits long and include a 3-digit area code.

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E.164 numbers were originally defined for use in the worldwide public switched telephone network (PSTN). The early PSTN collected routing digits from users and used the numbers to determine how to reach the called party.

The ITU-T E.123 standard provides guidance on printing E.164 telephone numbers, recommending the use of a plus sign (+) and spaces for digit grouping.

E.164 numbers have many benefits for international communications, including being an internationally recognized global standard, defining telephone number formats, and ensuring secure call delivery.

Here are some key benefits of E.164 numbers:

E.164 numbers ensure that you can reach any device on the PSTN and that calls are delivered properly.

To programmatically verify that a string is in a valid E.164 phone number, you can use the Twilio Lookup API or find international telephone input and validation in the Twilio Code Exchange.

Reasons to validate phone numbers include preventing fraud, ensuring deliverability, and validating previously collected phone numbers in a database.

A valid E.164 phone number must be a number up to fifteen digits in length starting with a '+'. This is according to the official ITU E.164 recommendation.

The format of a valid E.164 phone number can be matched using a regular expression, such as ^\+[1-9]\d{1,14}$.

However, this regular expression will also match numbers that are not valid phone numbers, so it's recommended to use the Twilio Lookup API for comprehensive phone number validation.

Here are some reasons to validate phone numbers:

E.164 is an international standard used to format phone numbers, and it's essential to use it when dialing international phone numbers.

The E.164 format is made up of a country code, area code, and subscriber number. For example, the US phone number 415 123 1234 is formatted as +14151231234.

Here's a breakdown of the E.164 format for the US phone number 415 123 1234:

You might have seen US phone numbers written as +13051234567 or UK phone numbers as +442045678910, which are examples of proper E.164 formatting.

Working with E.164 is a crucial aspect of international communications. To ensure that calls are delivered properly, it's essential to follow the proper format.

E.164 formatted numbers have a specific structure, with a country code, identification code, and subscriber number. The country code is typically 3 digits, while the identification code can range from 1 to 4 digits, and the subscriber number can be up to 12 digits minus the number of digits in the identification code. This structure is essential for successful routing of calls.

If you're working with phone numbers, it's crucial to validate them to prevent fraud and ensure deliverability. You can use the Twilio Lookup API to perform phone number validation and formatting without the need for RegEx. This can be done programmatically to validate previously collected phone numbers in a database or to ensure deliverability when sending a Twilio SMS or Voice call.

To validate an E.164 phone number, you can use one of the existing libraries or build your own validator using regular expressions. For example, the phone library in JavaScript can be used to validate phone numbers. Here's a breakdown of the E.164 format:

By following the E.164 format and validating phone numbers, you can ensure that calls are delivered properly and that each device has a unique phone number. This is especially important for international communications, where a globally recognized standard is essential.