For developers who maintain, extend or integrate with the plugin. It covers the architecture, the checkout, webhook, refund and subscription flows, the data the plugin stores, its safety mechanisms (signature checks, locking, idempotency), every hook, and how to develop and test locally.
Architecture
Design principles, compatibility, files, boot sequence, drivers, API clients, gateway and blocks.
Settings storage
The settings option, every key, and the helpers to read them.
Checkout flow
Order lines, the three checkout entry points, subscriptions, Billing transactions, Classic pay links and payment confirmation.
Webhooks
The endpoint, signature checks, Billing events, Classic alerts and multi-store tagging.
Concurrency and idempotency
Locks, fresh reads, markers, order completion, renewals and the refund ledger.
Refund internals
How refunds travel between WooCommerce and Paddle, and how chargebacks are handled.
Subscription internals
Linking, status mapping, renewal orders, the delayed link check and restrictions.
Customer invoice links
How invoice and receipt links are added to pages and emails.
Data reference
Order, subscription and user meta, options, transients, scheduled actions and uninstall.
Hooks reference
Filters and actions the plugin provides, with examples, and the hooks it uses.
Endpoints and front end
AJAX, admin-post and query endpoints, and the checkout scripts.
Local development and testing
Sandbox, tunnels for webhooks, logging, simulated webhooks and mocks.
Coding standards and releases
Coding standards and the release checklist.
Known limitations
What the plugin deliberately does not do, and why.
Licensing and the Lite upgrade
The license client, updates, and how Pro takes over from the free version.
For store owners
For setup and day-to-day use, start with Getting started instead.