Add items to inventory based on Xsolla solution

Xsolla provides a solution for the implementation of the player's inventory based on the In-Game Store product (Player Inventory). This solution allows you to sync all purchases and user premium rewards across platforms.

You can add items purchased using a third-party payment UI (e.g., Google Play In-App Purchase) to Player Inventory.

Items are added to the inventory when the Grant items to users API server query is called. If you are using Firebase for the back end of the application, use the ready-made cloud function:

  1. Add a Cloud Function to your Firebase project.
  2. Implement the logic for calling the function.

Add Cloud Function to Firebase project

  1. Initialize your Firebase project.
  2. Import and configure the function for adding items to the inventory where:

    • <MerchantID>Merchant ID found in Publisher Account:
      • In the Project settings > Webhooks section.
      • In the Company settings > Company section.
      • In the URL in browser address bar on any page of the Publisher Account. The URL has the following format:​merchant ID/Publisher Account section.

    • <ProjectID>Project ID found in Publisher Account:
      • Next to the name of your project.
      • In the Project Settings > Project ID section.

    • <ApiKey>API key found in Publisher Account in the Company settings > API keys or Project settings > API keys section.


For more information about working with API keys, see the API reference.

Key recommendations:

  • Save the generated API key on your side. You can view the API key in Publisher Account only once when it is created.
  • Keep your API key a secret. It provides access to your personal account and your projects in Publisher Account.
  • The API key must be stored on your server and never in binaries or on the frontend.

The function code for adding items to the inventory:

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const merchantId = "<MerchantID>";
const projectId = "<ProjectID>";
const apiKey = "<ApiKey>";

exports.redeem = functions.https.onRequest((request, response) => {
  const sku = request.body.sku;
  const quantity = request.body.quantity;
  const userId = request.body.user_id;

  const authHeader = Buffer.from(`${merchantId}:${apiKey}`).toString("base64");

  const postData = JSON.stringify(
        "comment": "Purchased by Google Pay",
        "platform": "xsolla",
        "user": {
          "id": userId,
        "items": [{
          "sku": sku,
          "quantity": quantity,

  const options = {
    hostname: "",
    port: 443,
    path: `/api/v2/project/${projectId}/inventory/reward`,
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "Content-Length": postData.length,
      "Authorization": `Basic ${authHeader}`,

  const req = https.request(options, (res) => {
    if (res.statusCode == 200) {
    if (res.statusCode == 404) {
    if (res.statusCode == 401) {

    res.on("data", (d) => {
  req.on("error", (e) => {


  1. Deploy the function to a production environment as per this example.

Call function from application

To add items to inventory, add logic to call the function from the application, specify redeem as the function name and pass the sku, quantity, user_id parameters to it.

Some billing interfaces (e.g., Google Play In-App Purchase) require initiating the logic for adding an item to inventory on the client side. In this case, implement a client-side method to call the redeem function.

As an example of implementation for Android, you can use the xsolla-googleplay-sdk module which allows you to add purchases from Google Play In-App Purchases to your inventory.

To apply the example in your project:

  1. Start Android Studio.
  2. Add the xsolla-googleplay-sdk module to your project.
  3. Initialize the library. To do this, add the following line to your Android project source code where <your-deployment-host> is the host of the cloud function URL (e.g.,

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The cloud function URL is displayed on the Firebase command line after running the function in production. Also, the function URL is available in the Firebase console in the Functions > Dashboard section.

  1. Implement the call of the InventoryAdmin.grantItemToUser (sku, userId, quantity, callback) method according to the application logic. The callback returns data on the success of the item being added to the inventory.

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Last updated: February 14, 2023

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