# Introduction

Welcome to the **Apaczka developer documentation**. The Apaczka API v2 lets
you price, create and manage courier shipments across 20+ carriers through a
single integration.

## How the API works

API v2 is an RPC-style API: every call is an HTTP `POST` carrying a
form-encoded envelope signed with **HMAC-SHA256**, and every response
comes back as HTTP `200` — the real outcome is in the response body.
Start with [Request signing](/legacy/hmac-signing) and
[Error semantics](/legacy/error-semantics), then browse the full
[API v2 reference](/reference/v2-legacy).

## Getting started

1. Get API credentials in the [Apaczka panel](https://panel.apaczka.pl)
   under **Settings → API**.
2. Follow the [Quick start](/quick-start).
3. Explore the [integration guides](/guides/authentication) for the full
   order lifecycle.

## SDK — the recommended way to integrate

The official **AlsendoOne SDK** for PHP
([`alsendo/alsendo-one-sdk`](https://packagist.org/packages/alsendo/alsendo-one-sdk),
[source on GitHub](https://github.com/Alsendo/AlsendoOneSDK)) is the
preferred way to integrate: it handles request signing and error mapping,
and exposes every API method through typed objects. Start with the
[PHP SDK guide](/sdk). Integrations in other languages call the API
directly — see [Request signing (HMAC)](/legacy/hmac-signing).