Insights & Resources • PUBLISHED 4/23/2020

What is an SMS API?

Learn the ins and outs of what an SMS API is, why it's useful, and what you should look for in an SMS API provider.

By Tony Furnas

SMS API explained

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

As there is usually a gap between the internet and SMS communications infrastructures, SMS APIs are used to connect web based applications and telecommunications carrier networks.

SMS APIs give web applications the ability to programmatically send and receive text messages over these networks.

SMS APIs allow developers to build powerful messaging capabilities into their applications that increase customer engagement, instead of needing to have a deep understanding of telecoms.

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By being highly configurable, easily consumable, scalable and cost effective, SMS APIs give developers the ability to focus on building the two-way communication experience that customers engage with most.

Sound interesting? You can buy a number and send your first message with Telnyx SMS API for free by signing up with your business email.

SMS API use cases

Business adoption of SMS has grown rapidly in recent years, with B2B SMS growing by 197% between 2015 and 2017 and A2P (Application to Person) SMS messages generating 75% of the total SMS market revenue. This growth is in response to the 80% of people using SMS in business related communications and the demand of consumers that would prefer SMS as opposed to traditional in person or voice conversations. To handle this growing adoption, businesses are utilizing SMS APIs that are built to integrate SMS into their applications with ease and adopt it for a wide range of use cases that can include:

  • Organizations that want to send critical alerts or important local public health information.
  • Integrating more security into your application with Two Factor Authentication.
  • Businesses looking to target their customers with marketing messages or special offers.
  • Internal business communications and sales lead alerts.
  • Companies that want to use SMS as a customer support option.
  • Sending important account notifications or delivery and order alerts.

A burgeoning telecom use case is Conversational AI, or in the case of SMS, chatbots. These allow machines and bots to handle minor customer issues and conversations before a person needs to get involved, thus saving time, manpower, and money. For developers building chatbots, SMS APIs allow them to build better customer experiences that deliver realistic interactions and create high-quality conversations.

How much does an SMS API cost?

SMS API costs can vary depending on what type of number you’re using to deliver your message. SMS or MMS messages sent over long code, short code, or toll-free will have different costs and this can be influenced further by where you’re sending the message, what provider you’ve decided to work with and what volume you are sending.

Also, some providers may charge you for inbound messages, so if you’re looking to utilize SMS as a two-way communication channel for support or chat these additional inbound charges can add up quickly as you will find it challenging to limit responses back to your numbers.

As a reference point, here’s a quick comparison of Telnyx pricing vs. Twilio:

To Send SMSTo Receive SMS
Number typeTelnyxTwilioTelnyxTwilio
Local Number$0.0025$0.0075Free$0.0075
Toll-Free Number$0.0055$0.0075$0.0055$0.0075
Short Code$0.0070$0.0075$0.0070$0.0075

It’s important to note that some US carriers will charge an additional fee when sending messages with local and short code numbers that may be passed back to you by your chosen provider.

What features should I look for in an SMS API?

Knowing what features you need when choosing a [SMS API provider]( is key. Some SMS APIs will be intrinsically simple while others will offer deep and developer-focused features. Having an idea of what you need will help, but knowing that your provider can scale with you and provide features as you need them is important as well.

The Telnyx SMS API offers a broad range of features that help developers build the application they want quickly and easily, while also increasing deliverability and creating a better customer experience.

Number Pool

Number Pooling will automatically select an outbound number for a message from a pool of numbers assigned to one of your messaging profiles. It maintains a balance across all of these numbers to ensure higher deliverability with all carriers. For sending A2P messages, Number Pooling via the Telnyx SMS API is designed to ensure your messages are being delivered the first time, every time.


Turning on the Geomatch feature with the Telnyx SMS API will help increase your deliverability and engagement by increasing the trust your customers have in the number they are receiving a message from. When customers are dealing with a local company, they expect that business to have a local number. Matching the area code of your customers will help increase the trust in the message, thus boosting engagement and improving the customer experience. When paired with Number Pool, Geomatch will automatically send messages from a number that matches the local area code of the recipient from within your pool of numbers.

Sticky Sender

For sending A2P (Application to Person) messages, turning on the Sticky Sender feature with the Telnyx SMS API will increase customer familiarity and trust, helping to make sure your messages are being read. Customers want to work with brands they know and trust, and by using Sticky Sender you can allow your customers to have a single and direct communications channel with you that’s easy to use.

Sticky Sender will automatically maintain sending messages from the same number to an individual customer each time allowing them to communicate with you through a single number, instead of having to track down different support or sales numbers. While you may have a large pool of numbers, maintaining this single touchpoint for each customer won’t overwhelm them by switching numbers with each new message.

Alphanumeric Sender ID

If you’re sending one-way marketing messages, Alphanumeric Sender ID will also increase the odds that your message is received and read by your customer as it helps to establish that the message is from your brand or company. 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. This makes your message easily identifiable to your customer, as you can set the ID to your brand name. (e.g., TELNYX).

URL Shortening

Telnyx provides a URL Shortening service with custom links to help you improve your brand awareness, increase trust and bypass spam filters that block most popular URL shortening sites. Any message that contains URLs with the supported domains will be converted into one of Telnyx's custom URLs. When URL Shortening is turned on, any messages that contain base URLs from the Telnyx supported URLs will be converted to a URL with a base domain of your choosing. In addition to URL shortening, you can also view how often recipients of your messages have opened the link via the Message Engagement Report. You can also track user engagement in real time by receiving webhooks when a custom link is clicked.

How does the Telnyx SMS API work?

The Telnyx SMS API is a set of REST APIs that allows developers to simply connect our external SMS interface into your existing infrastructure, to enable a smooth passing of commands and responses from your application to the interface and back for sending and receiving of SMS anywhere in the world.

What makes a good SMS API?

Above all, a good API should be easy to build with. However, your programmable SMS API should also offer you the scalability and flexibility you need to build the messaging app that fits your specific current and future needs.

SDKs and Robust Documentation

Software Development Kits (or SDKs) are a set of software development tools in one installable package. They’re designed to be used for specific platforms or programming languages and make building applications a far more streamlined process, requiring less development resources.

A good SMS API provider should deliver SDKs in specific programming languages i.e. Python, Ruby, .NET, Node, and PHP. These API wrappers mean you can easily integrate with the voice API, resulting in a faster go-to-market process for your application.

The same goes for developer documentation. Your SMS API provider should create robust documentation to cover a variety of use cases i.e. quickstart guides, tutorials and product overviews to ensure developers can build what they need quickly and easily.

Great Developer Support

Whether you’re building a simple or enterprise grade messaging platform, complications can arise. If you run into issues, you’re going to need technical support that matches your applications always on mentality, so finding an SMS API partner with 24/7 support at no extra cost is key.

Common Telnyx SMS API Questions

Telnyx is dedicated to building the best developer-focused experience possible, and the Telnyx SMS API was designed to do just that. By providing a powerful, scalable and easy to use SMS API, Telnyx gives developers the ability to design an SMS application that can increase engagement and deliverability to improve their customer’s experience.

Does Telnyx operate its own network?

Yes. As a software-driven licensed telecom operator with its own private, global IP network, Telnyx has the ability to deliver direct access to unmatched numbering resources and a deep inventory of numbers that allow customers to send SMS or content rich MMS across the globe with high deliverability and greater transparency into issues.

Does Telnyx provide reporting and analytics?

From reporting on the health of the numbers you use to send messages, to the deliverability and click-through rates of your messages, Telnyx provides the tools and reporting you need to make changes to your messaging strategy that can help you improve the quality of your customer experience.

What type of support does Telnyx offer?

Your business is always running, so we’re always on. Telnyx provides 24/7 support 365 days a year from our network operating centers in both Chicago and Dublin. Telnyx offers phone, email and live chat support for every customer, free of charge, so you can get the help you need whenever an issue comes up.

Is it easy to switch to Telnyx?

Absolutely. Telnyx developed the Twexit API to make switching your programmatic SMS services from Twilio to Telnyx easier than ever before. By making minimal changes to your Twilio messaging code, you’ll have greater deliverability, cheaper costs and better support in minutes.

Telnyx also allows you to bring your own number onto the Telnyx platform for programmatic messaging with Hosted SMS. The number remains with the current provider for voice, but routes all inbound and outbound SMS and MMS messages through the Telnyx network. This is especially useful for landline numbers that normally would not have messaging capabilities, meaning you’ll never miss a message from a customer again.

Get in touch with our team of experts to learn more about using the Telnyx SMS API, or check out the platform for yourself get started to buy numbers and send your first message. Or check out our developer documentation to see how it works.

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