> For the complete documentation index, see [llms.txt](https://ninjapay.gitbook.io/ninjapay-api-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ninjapay.gitbook.io/ninjapay-api-docs/how-to/api-reference-upi.md).

# API Reference (UPI)

Ninjapay API's allow web applications and developers to interact with Ninjapay platform systems. This guide will walk you through the primary methods that are part of the Ninjapay API.

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[Realtime Payment Links](/ninjapay-api-docs/how-to/api-reference-upi/plugins/realtime-payment-links.md)
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[Paywalls](/ninjapay-api-docs/how-to/api-reference-upi/plugins/paywalls.md)
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[Invoice](/ninjapay-api-docs/how-to/api-reference-upi/plugins/invoice.md)
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[Point of Sale - POS](/ninjapay-api-docs/how-to/api-reference-upi/plugins/point-of-sale-pos.md)
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[Build Your Own Plugin](/ninjapay-api-docs/how-to/api-reference-upi/plugins/build-your-own-plugin.md)
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