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Core Concepts: Numbers

Twilio gives you instant access to different number types in over 100 countries for your voice and messaging applications. A Twilio number can include different communication capabilities such as voice, SMS, MMS, and fax. You can programmatically manage these numbers and build complex IVR apps and chatbots using Twilio's REST APIs.

Long Code or Direct-In-Dial (DID) Numbers

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Direct Inward Dialing (DID) is a telephone service that allows call routing to a specific number at a business instead of going to a menu or a queue and dialing an extension. You can enable DID for your Twilio number by connecting your SIP infrastructure to a Twilio SIP Trunk or by registering your SIP endpoint on Twilio.

Long codes (which are 10-digit numbers in many countries) are meant for person-to-person communications, and can send 1 message per second. There are different concepts associated with a long code:

Local Numbers

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Local numbers are numbers which are assigned to a specific geographic region. These numbers are typically used by individuals and local businesses. For Twilio's recommendations on filtering for "local" numbers, see Purchasing Twilio numbers that are local to customers(link takes you to an external page).

National numbers(link takes you to an external page) are non-geographic long code numbers designed to be reachable from the entire country for the same price as a local phone call. Twilio offers national numbers in certain countries.

VoIP (Voice over IP) numbers are virtual numbers that get allocated to a user instead of a dedicated phone line. A virtual number is a standard number that is not locked down to a specific phone. You can use these numbers to route voice calls or text messages to any phone or workflow.

A mobile number refers to the 10-digit unique number that a wireless carrier uses to identify a mobile phone. Most countries (except for the US and Canada) assign a particular range for mobile numbers within the country's numbering plan so they can be easily distinguished from local numbers.

Toll-free numbers are numbers with distinct, preassigned 3-digit codes in place of an area code. They are often used for domestic inbound calls and are free for your customers.


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Twilio's US and Canada toll-free numbers are enabled for sending and receiving SMS messages. While most toll-free numbers are domestically reachable and aren't reachable from pay phones, US toll-free numbers can be reached from Canada.

Twilio offers toll-free numbers in various international countries. See Twilio international number availability and their capabilities(link takes you to an external page) for more details on availability and toll-free features. For details on country requirements and limitations, see Toll-free number restrictions and limitations(link takes you to an external page).

For a summary of different number types, see Phone Number Types and their Capabilities(link takes you to an external page).

You can use the Twilio Console or Twilio's REST APIs to manage provisioning, porting, and hosting your numbers with Twilio.

SIP Trunks connect IP-based communications infrastructure to the public switched telephone network (PSTN). Twilio's Elastic SIP Trunking(link takes you to an external page) uses the power of the cloud to bring instant provisioning, global reach (with local, national, mobile, and toll-free numbers in over 100 countries) and data-driven routing to the world of SIP Trunking. One way to procure a Twilio number is using the Twilio Console(link takes you to an external page). Alternatively, you can use the Phone Numbers 2010-04-01 REST API resources to search for, purchase, and manage your Twilio long code numbers:

Porting is the transfer of a number between two telephone service providers on behalf of an end-user. The process involves providing the right documentation to prove ownership of the number as well as coordination between the existing provider and the new provider with regard to the number's porting date.

"Port in" is the process of porting your number from your current provider to Twilio. When a port request is submitted to Twilio, Voice and SMS capabilities for the numbers are ported by default. Twilio supports porting of US and international numbers. You may port your numbers into Twilio via the Console(link takes you to an external page).

"Port out" is the process of porting your number from Twilio to a new provider. The Twilio Console has a Port Away Requests page(link takes you to an external page) with links to relevant "port out" resources.

Further Reading: Porting help articles(link takes you to an external page)

Hosted SMS allows customers to use Twilio's Programmable Messaging, Functions, and Studio products for sending and receiving SMS and MMS messages on voice-enabled numbers they already own as part of an established voice application. Twilio Hosted SMS supports USA & Canada in Beta.

Flex supports Hosted SMS via Flex Conversations. Hosted SMS is not available on Flex Legacy Messaging.

For a detailed guide on managing your Flex numbers, see Add and Configure a New Number with Twilio Flex(link takes you to an external page).

A short code is a special 5 or 6 digit number that is shorter than a long code number. Short codes are used to send two-way SMS and MMS messages. There are two types of short codes:

  • Regular : Random short code assigned to you which you cannot review in advance.
  • Vanity : A specific short code that you choose. For example, "MyBiz".

Twilio currently offers short codes in many countries around the world(link takes you to an external page) (provisioning time varies by country). Twilio short codes can send 100 messages per second by default. You can raise this limit for an additional fee.

Activation and Migration to Twilio

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Whether you're applying for a short code with Twilio or migrating one from an existing provider(link takes you to an external page), you need to start a short code application. Because short codes can send high volumes of messages, wireless carriers individually approve every short code for its intended use. For more details, see the help articles on short codes(link takes you to an external page).

Migration away from Twilio

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For guidance on migrating your Twilio short code to a different provider, see Transferring a short code lease away from Twilio(link takes you to an external page).

Free-to-End-User messaging (FTEU) is where the brand (the Twilio customer) pays the cost of sending an SMS to their end users. US short codes are the only way to send messages that are truly free to end users through Free-to-End-User messaging (additional fees and requirements apply). To learn how to programmatically send an SMS using a Twilio short code that you own, see the Programmable SMS Send Messages page.

A Premium SMS number is a 3-7 digit number used for messaging that charges a premium price to the end user per sent SMS. Twilio does not support premium SMS for short codes as they have historically been used as a vector for fraud and abuse.

A Sender ID is the name or number that identifies the sender of an SMS. This is defined by the "From" property of Twilio's Messaging resource. There are two types of Sender IDs:

There are two ways to activate your Twilio sender ID:

  • Dynamic: This refers to instant provisioning of a Sender ID and applies to most Twilio supported countries.
  • Pre-registration : Some countries require pre-registration, which means the Twilio customer has to provide information and sometimes additional documents, resulting in additional time before the Sender ID is activated. These Sender IDs are known as "pre-registered". For pre-registering a sender ID, visit Twilio's pre-registration page(link takes you to an external page) .

Further Reading: International Support for Alphanumeric Sender ID(link takes you to an external page)

Caller identification is a telephone service that transmits a caller's number to the called recipient when the call is being set up. In most cases, this will be the Twilio number(link takes you to an external page) or verified number(link takes you to an external page) used in the From parameter in your API request, or the callerId attribute of your TwimL <Dial> verb. For a detailed guide on addressing issues with caller identification, see Unable to Display a Business Name or Custom Text as Caller ID(link takes you to an external page).

Twilio and its customers need to comply with local regulatory requirements(link takes you to an external page) for their numbers. Twilio has made it easy for businesses to review their country's regulations and submit the required information and documents for compliance. To get started with regulatory compliance, see the Twilio Console or the Regulatory Compliance APIs quickstarts.

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