# Webhook S2S Postback

A Postback URL (or WebHook) is used by Publishers to receive conversions on their back-end servers and handle the reward to the users.

To set up a Postback URL in our Platform, go to **Settings** section and find the **Postback URL section** on the left.

<figure><img src="https://maf.ad/wp-content/uploads/2023/05/postback2-1-1024x683.png" alt=""><figcaption></figcaption></figure>

Here you can edit your URL and add parameters. Click the **Add Parameter** button to add more.

Make sure your URL is in a valid form:

```
https://yourdomain.com/?user_id={user_id}&payout={payout}...
```

On the right, you’ll see a list of **Macros** that are available to use in your Postback URL.

You can use the "Add Parameter" button to help you creating your Postback URL.

<figure><img src="https://maf.ad/wp-content/uploads/2023/05/postback-list2-1024x683.png" alt=""><figcaption></figcaption></figure>

Once you are done, click on **Save Postback URL**.

#### **Important Notes**

Please ensure the following requirements are met:

1. **HTTP Method Requirement**&#x20;

   All postbacks sent from our system use the **HTTP GET** method. Please ensure that your server accepts **GET** requests.
2. **Parameter Parsing**&#x20;

   Verify that your endpoint correctly parses all parameters in the Postback.
3. **IP Whitelisting**\
   Add all MAF postback IP addresses to your whitelist. In the next section (“Validating the S2S Webhook”) we will explain in detail how to configure this.
4. **Support for CPI Bidding Postbacks**
   * For CPI bidding offers, the publisher is paid only upon install.
   * For all subsequent events, your system must not reject postbacks with:
     * `payout = 0`
     * `user_payout = $X`\
       Ensure your platform supports this type of postback.
5. **Reward Calculation**&#x20;
   * **Do not use** the *virtual currency* parameter (`{user_payout_in_vc}`) to calculate rewards.
     * This parameter is provided **for informational purposes only**.
   * For accurate reward calculation, you must rely on one of the following parameters:
     * **`user_payout`**&#x20;
     * **`payout`** – the recommended parameter for reward calculation.
   * Reward conversion logic and final computation must always be handled on your side, based on either the `user_payout` or, preferably, the `payout` parameter.