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

# RelayOS: WhatsApp API for Transactional Messaging

> RelayOS lets you send transactional WhatsApp messages via Meta's official Cloud API. No ban risk, billed in BRL, with automatic retry and real-time webhooks.

RelayOS is a REST API that lets you send WhatsApp messages through Meta's official Cloud API. You get automatic retry with exponential backoff, real-time delivery webhooks, and pricing in Brazilian reais — with zero risk of account bans.

<CardGroup cols={2}>
  <Card title="Quick Start" icon="rocket" href="/quickstart">
    Send your first WhatsApp message in under 5 minutes.
  </Card>

  <Card title="Authentication" icon="key" href="/authentication">
    Get your API key and authenticate every request.
  </Card>

  <Card title="Guides" icon="book-open" href="/guides/send-message">
    Step-by-step walkthroughs for common use cases.
  </Card>

  <Card title="API Reference" icon="code" href="/api-reference/messages/send">
    Full reference for all public endpoints.
  </Card>
</CardGroup>

## How it works

<Steps>
  <Step title="Create a project and get your API key">
    Sign up and call `POST /v1/projects` to receive your API key instantly — no credit card required.
  </Step>

  <Step title="Connect your Meta credentials">
    Provide your Meta Phone Number ID and Access Token via `PUT /v1/projects/me/meta-credentials`.
  </Step>

  <Step title="Send your first message">
    Call `POST /v1/messages` with a recipient number and an approved template. RelayOS queues and delivers it automatically.
  </Step>

  <Step title="Receive delivery updates">
    Configure a `callbackUrl` to receive real-time webhook events as messages move from `QUEUED` to `DELIVERED` or `READ`.
  </Step>
</Steps>

## Key features

<CardGroup cols={2}>
  <Card title="Official Meta Cloud API" icon="shield-check">
    Built on Meta's official infrastructure — no unofficial clients, no ban risk.
  </Card>

  <Card title="Priced in BRL" icon="brazilian-real-sign">
    No exchange rate exposure. Pay in reais with transparent local pricing.
  </Card>

  <Card title="Automatic retry" icon="arrows-rotate">
    Failed deliveries are retried automatically with exponential backoff.
  </Card>

  <Card title="Real-time webhooks" icon="bolt">
    Get instant `POST` callbacks when message status changes.
  </Card>

  <Card title="Idempotency keys" icon="fingerprint">
    Pass an `Idempotency-Key` header to safely retry requests without duplicate messages.
  </Card>

  <Card title="Template variables" icon="brackets-curly">
    Personalize messages with dynamic variables in any approved WhatsApp template.
  </Card>
</CardGroup>