# Backend URL Configuration

## Overview

See [Backend URL Configuration](/paas/sdk/unified-vpn-sdk/setup/backend-url-configuration.md)

## Default URL Behavior

By default, the SDK follows these steps when deciding which URL to use:

1. If you add custom URLs using the `ClientInfo#addUrls` or `ClientInfo#addUrl` methods, the SDK will use those URLs first as these URLs have the highest priority.
2. If you do not provide any custom URLs, the SDK will use its built-in **production URLs** (the ones used in live environments).

{% hint style="info" %}

* The specific built-in production URLs are not mentioned in the SDK documentation.
* The SDK only includes production URLs by default. If you want to use the SDK in a staging or development environment (for testing), you need to provide the stage URLs yourself using either the `ClientInfo` methods or by adding a file named `pango_default_urls.json`.
  {% endhint %}

## Customizing Backend URLs

You can override the default production URLs by adding a new raw resource file named `pango_default_urls.json` to your Android project.

The `pango_default_urls.json` file should follow this structure:

```json
{
    "primary": [
        "https://url-1.net",
        "https://url-2.com",
        "https://url-3.com"
    ]
}
```

Specify your desired backend URLs in the `"primary"` array. The SDK will attempt these URLs in the order listed.

You can also provide an empty `"primary"` array to keep only the URLs specified via `ClientInfo`.


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