> For the complete documentation index, see [llms.txt](https://help.clickatell.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.clickatell.com/developers-api-reference/developers-archive/sms-http-s-api/http-s-api-overview.md).

# HTTP/S API Overview

Our simplest, most popular messaging API. This easy-to-use and powerful piece of code will quickly and easily integrate with your systems and applications, allowing you to send SMS messages internationally using our reliable bulk SMS messaging gateway.

## **Why use this API?**

* Extremely reliable and can be debugged easily, e.g. if you need to overcome a firewall problem.
* Can instantly send 50-100 messages in real time.
* Set up Delivery Acknowledgment, Sender ID and Message Delay.
* Supports text, Unicode, binary SMS and flash messages.
* Converts ringtones and logos into the correct format.
* Converts VCard and VCal.
* Supports extended length messages.
* Delivery acknowledgment and sender ID.
* Gateway escalation –  should your message be delayed for a predefined length of time, it can be escalated to an alternative delivery gateway; queuing lets you specify up to three prioritized queues on which your messages can be sent.
* Specify a delay of up to seven days when sending messages.
* Batch sending and two-way messaging.
* BONUS FEATURE: Conveniently check your message credits balance, query message delivery status, or redeem message credit vouchers through an API call.

## **When to use this API**

The HTTP/S API is ideal for keeping customers up-to-date about the latest changes in your business, whether it is a fantastic special offer or longer opening hours.


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