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

# API & Reference

- [Checkout Session API](https://docs.copperx.io/api-and-reference/checkout-session-api.md)
- [Invoice API](https://docs.copperx.io/api-and-reference/invoice-api.md)
- [Webhook Events](https://docs.copperx.io/api-and-reference/webhook-events.md)
- [Authentication & Security](https://docs.copperx.io/api-and-reference/authentication-and-security.md)