# Lydian Developer Documentation

> Accept cryptocurrency payments with Lydian. Start with hosted checkout, embed the Web SDK, or call the API directly.

Every page below links to a clean Markdown version of the documentation, generated from the same source as the website. Append `.md` to any documentation URL to get its Markdown (use `/index.md` for the home page). The complete documentation is available as a single file at https://developer.lydian.com/llms-full.txt.

## Get Started

- [Overview](https://developer.lydian.com/index.md): Accept cryptocurrency payments with Lydian. Start with hosted checkout, embed the Web SDK, or call the API directly.
- [Quickstart](https://developer.lydian.com/quickstart.md): Take your first payment in the Lydian sandbox: create a session, open hosted checkout, and confirm the transaction.
- [Choose Your Integration](https://developer.lydian.com/get-started/choose-integration.md): Decide between Lydian hosted checkout and embedded Web checkout — the two supported ways to collect a payment.
- [Authentication & Environments](https://developer.lydian.com/get-started/authentication.md): How Lydian authenticates API requests with API and Publishable keys, and the sandbox and production environments.
- [Use Docs with AI Agents](https://developer.lydian.com/get-started/ai-agents.md): Give AI coding assistants and agents clean, AI-readable Lydian documentation using llms.txt, llms-full.txt, and Markdown versions of every page.

## Guides

- [Accept Your First Payment](https://developer.lydian.com/guides/accept-a-payment.md): Take a crypto payment end to end with Lydian hosted checkout: create a session, open checkout, and confirm the transaction.
- [Web Checkout](https://developer.lydian.com/guides/web-checkout.md): Embed Lydian checkout directly on your site with the Web SDK, keeping customers on your own page.
- [Refund a Payment](https://developer.lydian.com/guides/refund-a-payment.md): Refund a completed Lydian transaction and understand how FX and gas fees affect the returned amount.
- [Set Up Webhooks](https://developer.lydian.com/guides/set-up-webhooks.md): Register a webhook endpoint so Lydian can notify your systems when payment events occur.
- [Handle Webhook Events](https://developer.lydian.com/guides/handle-webhook-events.md): Receive and process Lydian webhook events, and confirm payment state against the Transaction API.

## Core Concepts

- [How Lydian Payments Work](https://developer.lydian.com/concepts/how-payments-work.md): A mental model of the Lydian payment flow — how merchants, sessions, checkout, and transactions fit together.
- [Accounts & Merchants](https://developer.lydian.com/concepts/accounts-and-merchants.md): How Lydian accounts and merchants relate, how configuration is inherited, and why merchant context matters for API calls.
- [Sessions & Transactions](https://developer.lydian.com/concepts/sessions-and-transactions.md): The difference between a Lydian Session and a Transaction, and how the two relate during a payment.
- [API Key vs Publishable Key](https://developer.lydian.com/concepts/api-keys.md): The two Lydian credential types, how they differ, and where each is designed to be used.
- [Payment Lifecycle & Statuses](https://developer.lydian.com/concepts/payment-lifecycle.md): The states a Lydian payment moves through, and the meaning of the session and transaction status values.
- [Supported Cryptocurrencies & Networks](https://developer.lydian.com/concepts/supported-assets.md): The cryptocurrencies and blockchain networks Lydian currently supports for checkout, loaded live from the public assets endpoint.

## API Reference

- [Authentication](https://developer.lydian.com/api/authentication.md): The first step to using Lydian's API suite is to create an API token.
- [Accounts](https://developer.lydian.com/api/account.md): Read and update account-level configuration.
- [Merchants](https://developer.lydian.com/api/merchant.md): Lydian's API suite allows creating sub-merchants associated to the account.
- [Sessions](https://developer.lydian.com/api/session.md): Container to coordinate a payment from the customer to the merchant
- [Transactions](https://developer.lydian.com/api/transaction.md): Transaction for each crypto payment from the customer to the merchant.
- [Refunds](https://developer.lydian.com/api/refund.md)
- [Subscriptions](https://developer.lydian.com/api/subscription.md): Lydian's subscription API allows creating recurring billing plans and managing subscriptions.
- [Reporting](https://developer.lydian.com/api/reporting.md): Account-level reporting: volume summaries and transaction listings.
- [Webhooks](https://developer.lydian.com/api/webhooks.md): In this guide, we’ll look at how webhooks works. Lydian offers a way to listen to webhooks for different events.
- [Event Payloads](https://developer.lydian.com/api/webhooks/events.md): Payload reference for the events Lydian delivers to your webhook endpoints.
- [Reference Data](https://developer.lydian.com/api/reference.md): Public lookup endpoints: supported assets and countries.

## SDKs

- [SDK Overview](https://developer.lydian.com/sdks.md): Reference for the official Lydian SDKs, starting with the Web SDK (@lydianpay/sdk-web).
- [Web SDK](https://developer.lydian.com/sdks/web.md): Reference for the Lydian Web SDK (@lydianpay/sdk-web): installation, the lydian-checkout element, and window.Lydian.init.