SMS API

An SMS API (or SMS Gateway API) is a software interface that allows developers to build code that can send and receive SMS messages using an Application Programming Interface (API).

To get started, sign up for a Portal account, then follow the steps in our quickstart guide to buy an SMS-enabled number, create a messaging profile and start sending text messages.

An SMS API works by allowing developers to simply connect our external SMS interface into your existing infrastructure. This enables a smooth passing of commands and responses between your application to the interface and back, which allows you to send and receive SMS anywhere in the world.

Telnyx offers market-leading prices for feature-rich SMS, starting at just $0.004 to send an SMS on a local number. We currently do not offer free SMS, but you can easily add small amounts of money (e.g. $10) via credit card or even Bitcoin. You can find detailed pricing information here. Telnyx also offers even greater discounts as you scale, or when you’re ready to commit to monthly usage—talk to our sales team about your specific needs.

Yes, we provide SDKs in Python, Java, Node, Ruby, .NET and PHP, with more coming soon. These API wrappers help cut down integration time so you can get to market faster.

Telnyx has the ability to scale with you and supports large scale and broadcast messaging—just make sure your messages follow the Telnyx Acceptable Use Policy.

Yes, Telnyx supports rich media texting (MMS), so you can send images, gifs or videos as needed.

Absolutely! Short codes are perfect for sending and receiving high volume texts. You can find more information about Telnyx short code SMS here.

An alphanumeric sender ID lets you send messages using a custom ID constructed from a combination of alpha (a-z, A-Z) and numeric (0-9) characters as well as spaces. Companies can set their brand name as the ID (e.g. TELNYX), which makes it easy for the receiver to identify the sender. It's often used for sending one-way text messages, since the person receiving the message will be unable to reply with an Alphanumeric Sender ID.

You can integrate messaging into a range of different applications, including two-factor authentication, SMS marketing, political campaigns, customer support and more.

Carrier fees are passthrough fees charged by carriers in relation to numbers hosted on their network. These vary based on the sending number type, content sent and in certain cases compliance status. For example, AT&T charges a specific fee for unregistered 10DLC traffic sent to numbers hosted on its network. As of July 2023, Telnyx does not charge a markup on carrier fees.

Each number type has its own limitations and we recommend considering your use case in depth before choosing a number type. As a generalisation, for North American senders, 10DLC is the most commonly used, with Toll Free emerging as a high value alternative. Short Code is ideal for high volume, recognisable numbers, and Alphanumeric is used for 1-way international SMS notifications from a custom ID.

Inbound messages that don’t match a standard stop keyword are checked for opt-out intent. When a request like “please stop texting me” is detected with high confidence, Telnyx blocks the sender and sends your opt-out auto-reply, the same as a literal STOP. It’s off by default, enabled per messaging profile, and messages deliver normally if the AI is ever unavailable. Learn more in the AI opt-out detection release note.