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What is an SMS number? — SMS number types explained

A SMS number is a set of digits or characters that is used to address a text message (also known as SMS).

Michelle Bonsu
SMS Numbers and Traffic Types Explained
Since the popularization of mobile phones in the 1990s, SMS has become ubiquitous in our daily communications. Beyond person-to-person (P2P) conversations, SMS in business-to-customer (B2C) communications has become routine—from two-factor authentication messages to alerts and reminders and marketing campaigns. According to G2 Crowd, text marketing delivers results—SMS garners open rates as high as 98%. With higher engagement than email, it's not surprising that texting has become a core business strategy.
To make the most of your SMS communications, it's important to know what number and traffic types exist and how they differ. The types of numbers you use to send texts can impact message deliverability. B2C or application-to-person (A2P) SMS is governed by strict regulations—with significant penalties for non-compliance. In this guide, we’ll explore SMS number and traffic types, and tips on staying compliant with regulations.

SMS number types

Long codes

Long codes, also known as long virtual numbers, LVNs or long numbers, are 10-digit phone numbers that can send and receive global calls, faxes and SMS. They support two-way messages between businesses and customers, making them a great option for B2C and P2P communications. Due to their low throughput rate (i.e. the number of messages a number is able to transmit per minute, hour or day), long codes are best for non-marketing activities such as customer support and chat applications. There are two types of long codes:
  • 10DLC (10-digit long code): This refers to long codes that support A2P traffic. Some common forms of A2P SMS are appointment reminders, small-scale marketing campaigns and bank alerts. In 2021, AT&T, Verizon and other major U.S. carriers introduced restrictions on SMS marketing. Many carriers also provided new business registration requirements for A2P 10DLC marketing.
  • Local numbers: These are standard phone numbers that can send and receive calls, faxes and SMS. Businesses can purchase local numbers with Telnyx in over 200 countries. Number throughput may vary.

Short codes

Common short codes (CSC) are five- or six-digit phone numbers that companies and organizations use for Multi-Media Service (MMS) or SMS. Short codes are administered by the Cellular Telecommunications and Internet Association (CTIA) via the Common Short Code program. They have a high throughput rate and can support two-way messages, making them an optimal choice for large-scale marketing. Popular use cases include notifications, customer service and promotional messages within the U.S. and Canada. To avoid violating SMS regulations, organizations must ask customers for an explicit opt-in to receive messages and provide information on how to opt out.

Toll-free SMS

Toll-free numbers enable businesses to host calls and exchange text messages at no cost to their customers. Toll-free numbers support two-way messages and have distinct three-digit codes (eg. 800, 833). In the U.S., the Federal Communications Commission (FCC) assigns and regulates the use of toll-free numbers. Unlike short codes, toll-free numbers support both phone calls and SMS. Customers can respond to an SMS alert by texting or calling the same number. Toll-free numbers have a higher throughput rate than long codes but have a lower rate compared to short codes. As such, they’re commonly used in mid-scale marketing, customer support and notifications.

Alphanumeric sender IDs

Alphanumeric sender IDs allow businesses to send one-way messages to customers. Unlike two-way messages that can send and receive SMS, customers can’t respond to one-way messages. An alphanumeric sender ID consists of a custom combination of letters (a-z, A-Z), numbers (0-9) and spaces. Companies can create IDs using brand names (e.g., TELNYX) so customers can easily identify them.
Alphanumeric sender IDs use up to 11 characters and are ideal for non-U.S. and Canada notifications and two-factor authentication (2FA). Not all countries support alphanumeric sender IDs and some have pre-registration requirements; therefore, it’s important to learn each country’s availability and process before registering with a communications provider.
SMS number types
Long codesShort codesToll-freeAlphanumeric sender ID
Number length10 digits5 or 6 digits10 digitsUp to 11 characters
Correspondence capability2-way2-way2-way1-way
Use casesCustomer service, chatbotsNotifications, customer service and promotional messagesCustomer support and notificationsNotifications and 2FA
Number capabilitiesCalls and SMSSMS and MMSCalls and SMSSMS

SMS traffic types

With the Telnyx SMS API, you’re free to select the SMS traffic type that best suits your needs. This will be either A2P or P2P.
Application-to-person (A2P) messages are sent from an application to a person. They’re popular in marketing campaigns and used to deliver automated alerts, notifications or reminders.
Person-to-person (P2P) messages are sent from one person to another. This is common in customer support and allows agents to respond to customer queries. P2P may also be used internally to facilitate communication between staff.
If you’re unsure of which number and traffic type applies to your use case, CTIA’s Messaging Principles and Best Practices offer a set of recommendations to help guide your decision. Regardless of which number and traffic type you choose, ensure you’re compliant with SMS regulations. Stay informed on changes in regulations and maintain best practices with our SMS regulations guide.

How to view and change your SMS traffic type with Telnyx

With the Telnyx SMS API, you can reach customers around the world using triggered SMS alerts. You can choose from local and toll-free numbers, short codes, or alphanumeric sender IDs. Telnyx offers a deep number inventory, compliant global communications and an intuitive Mission Control Portal so you can easily view and change your SMS traffic type.
Viewing and changing your SMS traffic type can be accomplished in five simple steps:
  1. Sign in to the Telnyx Mission Control Portal.
  2. Click on Numbers in the navigation menu on the left-hand side of the portal.
  3. Click the routing button [⇄] next to the number you want to check.
  4. Review your traffic type under Messaging Properties.
  5. To change your traffic type, select either the A2P or P2P radio button and then click Save Changes.
Note: You can only choose traffic type if your numbers are eligible for both A2P and P2P traffic.

Purchase numbers from Telnyx and start sending texts in a matter of minutes. Follow our easy setup guide to get started.
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