SMS Glossary

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A2P: Application-to-Person (A2P) messaging is any kind of message traffic in which a person receives messages from an application rather than another individual, and when it is typically not expected to receive a reply. A2P message includes, but is not limited to, marketing communications, appointment reminders, chat bots, notifications, and one-time passwords (OTPs) or PIN codes.

Aggregator: an SMS aggregator is a link between carriers and software. They build and maintain the technical relationships with wireless carriers. An aggregator is a third-party who connects via the Short Message Peer-to-Peer (SMPP) directly to the wireless service provider in order to offer services to consumers on behalf of content providers. 

Alphanumeric sender ID: see Branded sender ID.


Branded sender ID: a type of SMS sending number used in the UK and Australia; it cannot send MMS messages or receive any text messages. The sender ID can be customized to match your brand. 


Carrier: also referred to as a mobile or wireless carrier. Carriers provide cellular services, allowing phones and tablets to connect with each other. AT&T, T-Mobile, and Verizon are all wireless carriers.
Clicked SMS: metric for when a recipient clicks on a link within an SMS message.
Consented to Receive SMS: metric for when a recipient confirms that they want to receive your messages.
CTIA: stands for Cellular Telecommunications Industry Association. The CTIA is a trade organization run by wireless companies such as AT&T, Verizon, etc. It established the short code system and provided guidelines against SHAFT (see entry below).

Custom keyword: a type of keyword that you create in Klaviyo to allow customers to subscribe to your SMS marketing efforts. Custom keywords must be between 3 and 20 characters and only include alphanumeric characters. They cannot be words that people commonly use in normal text conversations (e.g., is, are, can, will, his, there, why, the, about, etc.) or that pertain to SHAFT or illegal activities (e.g., CBD). 


Failed to Deliver SMS: metric for when a message is sent but not delivered to the recipient.
Filtering: when a message is not delivered by a wireless carrier. Wireless carriers filter SMS and MMS messages they believe may be spam or do not meet content requirements (e.g., includes terms related to SHAFT or CBD).


Keyword: also known as just keyword response. These are words that, when sent by a subscriber, prompt a certain action and an automated response. For instance, if a subscriber texts “STOP,” they will automatically be unsubscribed from receiving SMS from your brand and a message will go out informing them of this action. Other examples of keywords are HELP, INFO, CANCEL, and QUIT. Keywords are not case-sensitive.


Long code: also called a long number. It is a type of SMS and MMS sending number consisting of 10 digits and looks like a regular phone number (1-XXX-XXX-XXXX). 


MMS: stands for multimedia message service. This is a type of text message that includes multimedia, such as an image or GIF.


Received SMS: metric for when Klaviyo has recorded that your recipient has received an SMS.


Sent SMS: metric for when someone texted your destination number to subscribe.
SHAFT: stands for sex, hate, alcohol, firearms, and tobacco. Using terms related to SHAFT or anything illegal, including CBD, will cause a message to be heavily filtered by wireless carriers.
Short code: a type of SMS and MMS sending number consisting of a short series of numbers (XXXXX). Short codes are subject to less filtering than other number types and can quickly send to a large number of recipients.
SMS: stands for short messaging service. This is a type of text message that includes only text or symbols such as emojis.
Subscribe keyword: a type of keyword your customers can use to opt into receiving SMS marketing messages from your brand. One example is JOIN, which is the default in Klaviyo. Subscribe keywords can be customized to fit your brand (see: custom keyword).


TCPA: stands for the Telephone Consumer Protection Act. This act covers the use of automated telephone communications, including phone calls, voicemails, fax machines, and text messages. Under TCPA, sending spam text messages is illegal and can result in fines.
Toll-free number: a type of SMS sending number consisting of 10 digits starting with an eight (1-8XX-XXX-XXXX). Toll-free numbers can be verified, which makes them subject to less filtering than long numbers. You can only have one toll-free number per account.


Unsubscribed from SMS: metric for when a recipient texts STOP and unsubscribes from your SMS messages.


Vanity short code: type of short code that allows you to choose what the number is (XXXXX).


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