# Octany for Developers

> Developer documentation for integrating Octany — the Swedish billing
> engine for subscriptions, one-off orders, hosted checkout, donation
> embeds, and signed webhooks.

## Pages

- [Overview](index.html): integration paths, billing concepts, REST endpoint overview.
- [Fundraising](fundraising.html): Donation, 1-click Swish, and Greeting embeds for campaign pages, editorial pages, and seasonal giving.
- [Checkout](checkout-v2.html): hosted checkout URL + query params, success/redirect handling, `window.Octany` JavaScript API, and embeddable cart.
- [Classic widget](classic-checkout.html): classic `<octany-widget>` custom element, attribute reference, iframe vs. button modes, postMessage protocol, and multi-product tabs.
- [Webhooks](webhooks.html): event catalog (`subscription.*`, `order.*`, `product.*`), example payloads, HMAC-SHA256 verification recipes, and delivery semantics.
- [API](api.html): human-readable REST API reference with endpoint groups, request bodies, response examples, and resource payload shapes.

## Key Rules

1. Use [Fundraising](fundraising.html) for modern donation experiences: Donation, 1-click Swish, and Greeting.
2. Use [Checkout](checkout-v2.html) for hosted checkout, cart, and app-driven payment flows.
3. Use [Classic widget](classic-checkout.html) only for existing classic integrations.
4. Webhooks are the source of truth for payment completion. Never trust the success-page redirect alone.
5. Correlate via `reference_id`, which comes from the `referenceId` you set when constructing the checkout URL.

## Machine-Readable Docs

- [docs/frontend.md](docs/frontend.md)
- [docs/integration.md](docs/integration.md)
- [docs/webhooks.md](docs/webhooks.md)
- [docs/openapi.yaml](docs/openapi.yaml)