# Custom Integrations

import { Steps } from '@astrojs/starlight/components';
import Image from '@components/content/Image.astro';

Guides in this section cover the basics of SumUp APIs, allowing you to develop a custom integration if SumUp products don't fully support your use case.

## Getting a Sandbox Merchant Account

Create a sandbox merchant account to test APIs without real money:

<Steps>

1. Log in to your SumUp account.

2. Open the drop-down menu between **Support** and your user panel.

3. Select **Sandbox Merchant Account**. Your merchant account is now switched to sandbox mode.

</Steps>

<Image alt="A screenshot of the account selection dropdown in the SumUp dashboard with the sandbox merchant account highlighted with red circle" src="/img/guides/test_acc.png" width="40%" />

With your sandbox merchant account, begin making API calls with real data. Sandbox merchant accounts **do not** process transactions with real funds. The sandbox merchant account has a different ID and displays a clear warning. Requests with a value of 11 (in any currency) always fail by design, to test failed transaction scenarios.

<Image alt="A screenshot of the dashboard with sandbox merchant account selected" src="/img/guides/test-account-warning.png" width="100%" />

When finished experimenting with the sandbox merchant account, switch back to a regular account for business purposes.

SumUp provides official SDKs for Node.js, Go, Python, Java, PHP, .NET, and Rust — visit the [SDKs overview page](/online-payments/sdks/) to choose the client that fits your stack.