> 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/reference/clickatell-api-reference.md).

# Clickatell API Reference

Elevate your business interactions in chat with Clickatell's powerful APIs.

## Channels

* [WhatsApp and SMS (One API)](/developers-api-reference/reference/one-api.md):  Communicate with customers via multiple messaging channels (WhatsApp and SMS) using a single integration.
* [SMS only](/developers-api-reference/sms-api.md): Enable one- and two-way SMS communication with your customers.

## Applications

* [Chat 2 Pay](/developers-api-reference/chat-2-pay-api.md): Send payment requests to customers and facilitate payments via chat for secure, contactless payment experiences.
* [Chat Flow](/developers-api-reference/chat-flow.md): Direct customers to an external web page from within a Chat Flow conversation and return with additional data. 


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