WHMCS 9.0 Expanded API Coverage: Buy Flow & Cart API 2026

WHMCS 9.0 includes expanded API coverage for the buy flow: cart, checkout, and order creation. The new API is built on OpenAPI and JSON:API standards, with RESTful methods and UUID support, so developers can build custom order flows, static frontends, and CDN-delivered experiences. This guide summarizes what's available and why it matters.

Buy Flow API. Unlocked.

Built on OpenAPI and JSON:API standards, the new API supports product listing, cart actions, and order creation with RESTful methods and UUID support.

Designed for modern deployment, including static frontends and CDN delivery, giving your developers more control without compromising core stability.

What the Expanded API Covers

RESTful methods — Aligned with OpenAPI and JSON:API specifications
UUID-aware — Consistent identifiers for future scalability
Product listing, cart actions, order creation — Full control over the buy flow
Static frontends — Build and deploy frontends that call the API, including via CDN
Well-documented — Easier to test and integrate with modern tooling

Who It's For

Mid-to-large WHMCS users and developers who want to:

Build custom ordering or checkout experiences
Use a separate frontend (e.g. React, Vue) with WHMCS as the backend
Deploy storefronts on CDNs for performance

This update gives you the tools to build and optimize purchase flows in line with modern development practices.

Nexus Cart — default modern cart experience
WHMCS 9.0 Release Guide

WHMCS 9.0 Expanded API Coverage: Buy Flow & Cart API 2026