> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ionicfi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# API overview

> How the Ionic API is organized and where to find endpoint details.

The customer-facing API reference is split into lightweight orientation pages and generated endpoint pages.

Use orientation pages to understand the model and lifecycle. Use endpoint pages for exact methods, paths, authentication, headers, parameters, request payloads, response payloads, examples, and error shapes.

## Start with these

| Area              | Overview                                                  | Endpoint examples                                                                                                                                                                                                                                                    |
| ----------------- | --------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Checkout          | [Checkout sessions](/api-reference/checkout-sessions)     | [Create checkout session](/api-reference/checkout-sessions/create-a-checkout-session), [Confirm checkout session](/api-reference/checkout-sessions/confirm-a-checkout-session), [Get checkout session](/api-reference/checkout-sessions/retrieve-a-checkout-session) |
| Payment links     | [Payment links](/api-reference/payment-links)             | [Create payment link](/api-reference/payment-links/create-a-payment-link), [Update payment link](/api-reference/payment-links/update-a-payment-link)                                                                                                                 |
| Catalog           | [Catalog](/api-reference/catalog)                         | [Create product](/api-reference/products/create-a-product), [Create price](/api-reference/prices/create-a-price)                                                                                                                                                     |
| Customers         | [Customers](/api-reference/customers)                     | [Create customer](/api-reference/customers/create-a-customer), [Update customer](/api-reference/customers/update-a-customer)                                                                                                                                         |
| Payment intents   | [Payment intents](/api-reference/payment-intents)         | [Create payment intent](/api-reference/payment-intents/create-a-payment-intent), [Get payment intent](/api-reference/payment-intents/retrieve-a-payment-intent)                                                                                                      |
| Refunds           | [Refunds](/api-reference/refunds)                         | [Create refund](/api-reference/refunds/create-a-refund), [Get refund](/api-reference/refunds/retrieve-a-refund)                                                                                                                                                      |
| Terminal payments | [In-person terminal payments](/guides/in-person-payments) | `POST /terminals/{id}/process_payment_intent`, `GET /terminal_payments/{id}`                                                                                                                                                                                         |
| Invoices          | [Invoices](/guides/invoices)                              | `POST /invoices`, `GET /invoices/{id}`                                                                                                                                                                                                                               |
| Subscriptions     | [Subscriptions](/guides/subscriptions)                    | `POST /subscriptions`, `GET /subscriptions/{id}`                                                                                                                                                                                                                     |
| Credit notes      | [Credit notes](/guides/credit-notes)                      | `POST /credit_notes`, `GET /credit_notes/{id}`                                                                                                                                                                                                                       |
| Saved cards       | [Save a card for later](/guides/save-cards)               | `POST /setup_intents`, `POST /setup_intents/{id}/confirm`                                                                                                                                                                                                            |
| Webhooks          | [Webhooks](/webhooks/overview)                            | `POST /webhook_endpoints`, `GET /webhook_endpoints/{id}`                                                                                                                                                                                                             |

## Shared behavior

| Topic                                                             | Why it matters                                                                |
| ----------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| [Authentication](/api-reference/authentication)                   | Server-side requests use secret keys. Hosted checkout URLs stay buyer-facing. |
| [Request and response shape](/api-reference/request-response)     | Common resource shape, timestamps, nullability, and metadata.                 |
| [IDs](/api-reference/ids)                                         | Prefixes such as `cs_`, `pl_`, `prod_`, `price_`, `cus_`, and `rf_`.          |
| [Idempotency](/api-reference/idempotency)                         | Safe retries for create and refund requests.                                  |
| [Errors](/api-reference/errors)                                   | Standard error envelope and payment decline details.                          |
| [Pagination](/api-reference/pagination)                           | List endpoint pagination patterns.                                            |
| [Rate limits](/api-reference/rate-limits)                         | Headers and retry behavior.                                                   |
| [Backwards compatibility](/api-reference/backwards-compatibility) | How the API evolves without breaking integrations.                            |