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

# Introduction

> Overview of the Zapyd REST API for payins, payouts, KYC and webhooks.

This section covers core concepts for calling the Zapyd API: where requests go, how authentication works, how webhooks behave, and how to handle retries safely.

## What you can build

Use the API to move between fiat and stablecoins for your customers: **pay-in** (on-ramp), **pay-out** (off-ramp), **KYC**, **bank accounts**, and **webhooks** for status updates.

<CardGroup cols={2}>
  <Card title="Quickstart" icon="bolt" href="/guides/getting-started/quickstart">
    A signed request helper and a complete sandbox order in about 10 minutes.
  </Card>

  <Card title="Guides" icon="book" href="/guides/getting-started/overview">
    Step-by-step flows for onboarding, payins, payouts, cross-border payments and going live.
  </Card>
</CardGroup>

## Next steps

<Steps>
  <Step title="Pick an environment" icon="server">
    Use sandbox for development and production when you go live. See [Core concepts](/guides/getting-started/core-concepts#environments-and-base-urls).
  </Step>

  <Step title="Authenticate requests" icon="key">
    Every call uses signed headers. See [Authentication](/api-reference-exchange/overview/authentication).
  </Step>

  <Step title="Handle events" icon="bell">
    Subscribe to [Webhooks](/api-reference-exchange/overview/webhooks) and design handlers to be [idempotent](/api-reference-exchange/overview/authentication).
  </Step>
</Steps>


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