This guide is suitable for both developers and line-of-business professionals. If you want to start experimenting with the APIs right away, check out the Programmable SMS Quickstarts.
Choosing a phone number type will be one of the first, and most important, decisions you make in your SMS onboarding journey. Which number type you choose will dictate your business costs, message throughput, which regulatory requirements you will have to follow, and the level of carrier filtering you may experience.
It can be tempting to choose a number type based on preference or aesthetic, but it will be in your best interest to review and analyze the benefits and weak points of each to determine which is best for you. Choosing the wrong number type can often lead to increased filtering, errors, and cost, bringing you back to the drawing board down the line.
In this guide, you will walk through the decision-making process for choosing the type of number that best suits your business needs. You'll also identify the next steps to take to provision that number.
The WhatsApp use case won't be addressed in detail here, but the WhatsApp Business API guide is a good place to start if you think that might be part of your strategy.
It can help to think about phone number types on a spectrum of cost versus filtering. Lower cost numbers such as US A2P 10DLC (application-to-person 10-digit long code) will have a higher chance of getting filtered depending on the content and send volume. A US A2P 10DLC phone number is the easiest entry point for sending messages, but as you increase your message volume it may be in your best interest to review high throughput toll-free (HTTF) or short code phone numbers.
Here are a few questions you should ask yourself when choosing your number type:
If you intend for your customers to immediately receive your messages you will need high throughput, or the ability to send a large volume of messages per second (MPS). A good example of why you might need high throughput is if you send urgent communication, such as a weather advisory from a government agency. In this scenario, you may need to ensure that thousands of messages are delivered straight away.
Number types that are capable of high throughput are high throughput toll-free (HTTF) and short codes.
Opting for a low throughput number, such as toll-free or US A2P 10DLC, will cause queue and message delivery delays when you exceed the limits on message segments per second. For some messaging programs, these queues may not be problematic. These numbers are quicker to provision and less costly to implement – they can be a great match for some use cases.
If you need to start sending messages as soon as possible, short codes may not be an option. Applying for and provisioning a short code can take six to twelve weeks. It involves a rigorous application process that provides high throughput and low filtering once complete, but your business might not be able to allow this much time to provision a number. You can provision a US A2P 10DLC number in less than an hour, with just a few pieces of business information.
The concept of volume in messaging refers to the number of messages you plan to send, usually calculated on a daily or monthly basis. We typically recommend choosing a number type that can handle your peak daily or monthly volume - such as during holiday sending for retail, or election times for governmental and political organizations. You can consult our rate limits and messaging queues to determine where your volume might sit relative to number types available through Twilio.
In broad terms, low volume sending means you can opt for lower cost phone number resources such as US A2P 10DLC or verified toll-free. For high volume sending, HTTF and short codes will be better suited to your use case.
Texting regulations vary by country. Your choice of number type might not be available in the countries from which you plan to send. You can review the SMS regulatory guidelines page for the countries in question before making any decisions on number types. If you find that none of the number types available within a country fit the needs of your business, you might want to consider using WhatsApp. See below for more details on implementing WhatsApp.
In addition to the considerations shared above, you also need to define which capabilities the phone number needs to have. The decision tree below breaks down the questions you should answer before choosing your phone number.
All number types provide one-way and two-way communication capabilities in the United States.
Regulations vary significantly country by country, and some numbers are not allowed in certain countries. To determine what numbers are available for sending to and within specific countries, please consult the SMS regulatory guidelines page.
In general, keep in mind that in some countries your chosen number type may be overwritten–that is, the number will not appear to the recipient as you intended–so it's worthwhile understanding this before making a choice. Additionally, some countries require an Alphanumeric Sender ID, which provides strong deliverability, brand recognition, and good open rates, but it only allows for outbound communication.
With all of that in mind, a WhatsApp integration is often a strong alternative for international messaging.
Regardless of where you are sending from or to, we recommend Twilio Verify for all 2FA use cases. Check out the Twilio Verify documentation for more information.
Toll-Free is a great option if you want one number for both text and call communications. This way customers can start an interaction on SMS and transfer easily to a phone call.
To get started, purchase a toll-free number via the Twilio Console or API, then start the verification process. The verification process is free and reduces the risk of message filtering on all major networks in the US and some in Canada.
High Throughput Toll-Free (HTTF) is a great option when you want to utilize a Toll-Free number for your sending but need more than the default 3 MPS (messages per second) for standard Toll-Free numbers. Other than the increased throughput, there is no difference between an HTTF and a Toll-Free number.
To get started, first follow the same process for purchasing a toll-free number and start the verification process. Once the verification process is complete, you can reach out to your Account Executive to start the throughput increase process that will turn your toll-free number into an HTTF.
Short for Application-to-Person Ten-Digit Long Code, US A2P 10DLC is a low cost and quick-to-provision number type capable of sending to United States phone numbers that can be localized; in other words, you can select an area code that mirrors your customer’s local region. You can get decent throughput with US A2P 10DLC–the exact amount varies based on your company size, but can be up to 225 MPS. It offers two-way messaging, and is MMS capable-that is, it can send multimedia messages (e.g., photos, videos, emojis, and weblinks).
To get started, purchase a phone number through the API or the Console then follow the documentation to register your US A2P 10DLC phone number.
The registration process will involve the following three steps.
A short code is a five- to six-digit number used to send and receive messages. Short codes provide the highest performance of any number type. They enable high throughput with minimal filtering, resulting in the best delivery of messages. Short codes require an application process that comes with one-time and recurring fees. They are the most expensive, and they take six to twelve weeks to obtain, but the burden of the cost and timeline is balanced by excellent performance thereafter.
WhatsApp does not require a cellular network connection, but instead connects to the internet. For this reason, it's sometimes called an “Over The Top” (OTT) application. It’s popular in many countries and offers a great alternative to the types of numbers featured above. If you would like to learn more about implementing with WhatsApp, navigate to the resources below to get started: