> For the complete documentation index, see [llms.txt](https://docs.ecommerce.seb.ee/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ecommerce.seb.ee/integration/api-client-sdk/overview.md).

# Overview

Learn supported SDK languages, API coverage, access requirements, capabilities, and alpha support.

The **API Client SDK** is a collection of server-side libraries for integrating with the **Merchant API**.

The SDK runs entirely on your backend and provides strongly typed, language-specific clients that wrap:

* HTTP communication
* OAuth 2.0 client authentication
* JWE card data encryption
* JSON serialization and deserialization
* Webhook notification processing

Instead of working directly with raw REST requests, developers interact with strongly typed request and response models.

***

## Your Responsibilities

The SDK simplifies communication with the Merchant API, but your application remains responsible for:

* Hosting your backend application.
* Managing customer redirects and return pages.
* Protecting API credentials.
* Providing a publicly accessible HTTPS endpoint for webhook notifications.
* Managing your order lifecycle and business logic.

{% hint style="info" %}
The SDK is designed for server-side applications only. It must not be used directly from browser-based or mobile client applications because it requires secure handling of API credentials.

The SDK does not render customer-facing checkout pages.

For Hosted Checkout or browser-based integrations, see **Hosted Checkout** documentation.
{% endhint %}

***

## Supported Languages

The SDK is currently available for:

| Language             | Primary Dependencies                                                |
| -------------------- | ------------------------------------------------------------------- |
| Java                 | Jackson, Nimbus JOSE+JWT, SLF4J API                                 |
| PHP                  | Guzzle 7, web-token/jwt-library 3, ReactPHP HTTP (Webhook Listener) |
| C# / .NET            | jose-jwt, System.Text.Json                                          |
| Node.js / TypeScript | axios, jose                                                         |

{% hint style="info" %}
All language implementations provide the same functional API coverage.
{% endhint %}

***

## API Coverage

The SDK provides complete coverage of the **Merchant API v1**, including:

* Payment initiation (CIT and MIT)
* Payment information
* Captures
* Cancellations
* Refunds
* Refund reversals
* Hosted Checkout sessions
* Pay by Bank
* Click to Pay
* Token management
* EMV® 3-D Secure
* Shop information
* Webhook notifications

There are currently no unsupported Merchant API operations.

***

## Supported Environments

The SDK supports both Sandbox and Production environments.

| Environment | Purpose                                          |
| ----------- | ------------------------------------------------ |
| Sandbox     | Development, testing, and integration validation |
| Production  | Live payment processing                          |

Environment selection is performed by configuring the appropriate API base URL.

***

## SDK Capabilities

The SDK provides built-in support for:

* OAuth 2.0 client credentials authentication
* Automatic access token caching and renewal
* JWE card data encryption
* Strongly typed request and response models
* Webhook notification handling
* Consistent error handling
* Pluggable HTTP client, serializer, encryption, and logging implementations

{% hint style="info" %}
Additional implementation details are described in the **Guides** section.
{% endhint %}

***

## Versioning & Support

The SDK follows **MAJOR.MINOR.PATCH** semantic versioning.

All language implementations within the same SDK release share the same version number.

The SDK targets **Merchant API v1**. API version selection is not configurable.

## Distribution

Each language SDK ships as a checksum-verified ZIP archive, not a package-registry release. See [Distribution](/integration/api-client-sdk/overview/distribution.md) for the verification steps and per-language installation links.


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