---
title: "SMS APIs in Insider One"
slug: "sms-api-overview"
description: "Understand how transactional SMS works: messages triggered by user actions (like OTPs, alerts, and receipts) that Insider delivers with high reliability and minimal opt-out risk."
updated: 2026-05-11T19:38:10Z
published: 2026-05-11T19:38:10Z
canonical: "academy.insiderone.com/sms-api-overview"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://academy.insiderone.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SMS

Transactional SMS messages are automatic messages triggered by a particular customer's actions. They do not have marketing motivation. Instead, they typically contain necessary or important information such as receipts, delivery details, updates, order confirmations, and more. Since a customer's unique actions trigger these messages, they are always sent individually rather than in a large list. With this SMS type, you can support your user base with important notifications and maintain their engagement.

You do not need opt-out information because these SMS messages contain static information, such as system messages, password recovery messages, welcome messages, or other important updates.

You need to set up the [Transactional SMS API](/docs/send-transactional-single-sms) to send transactional SMS messages, and it will continue to work thereafter.

Thanks to the [OTP / Verify API](/docs/otp-for-sms), you can also generate, send, and verify One-time password (OTP) codes for the SMS channel.