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User account linking

If you decide to keep alternative sign in providers (Google or Facebook for example) for users playing on CrazyGames, you will need to implement account linking between them and the CrazyGames user account.


This is an advanced integration scenario. Improper integration may delay the release of your game or can lead to it being rejected. We support the user flows described below. If you want to support additional functionality e.g. merging or migrating user accounts, we can not provide technical support.

These are the user flows we expect you to support in order to ensure a consistent experience for CrazyGames users.


Rather than using a CrazyGames account as an identifier, you will need to create and maintain a mapping in your back-end between

CrazyGames accounts and in-game account identifiers. If you are using Firebase, please refer to this section.

At game launch

Start by retrieving the current user. The game should request the current user account every time the game starts.

User is not logged in (getUser() returns null)

You should always allow the user to start playing as Guest.

Optionally, you can give the user the choice:

  • 'Login with CrazyGames' button (triggering our Auth prompt method), or other login methods (Google, Facebook, etc.)
  • Continue as Guest

Please note:

  • Don't trigger the Auth prompt automatically as this might confuse the user
User is logged in on CrazyGames (getUser() returns a user)

Check if the CrazyGames account (via getUserToken()) is already linked to an in-game account in your back-end.

  • Case: There is a game account linked to this CrazyGames account
    • Fetch the data for this user from your back-end, and start playing!
    • A Logged-in CrazyGames account should always take the highest priority over in-game accounts.
  • Case: There is not yet a game account linked to this CrazyGames account
    • Automatically create a game account that is linked to the player's CrazyGames account, based on the user token. This user will have fresh data in your back-end.
  • Case: The user is logged in in-game but not yet linked with CrazyGames account
    • Display a button "Link CrazyGames account" that will prompt the user to link the account or create a new account. See account link prompt
    • We advise to link with "fresh" accounts only and avoid merging, or as an alternative, making users choose which data to keep.
    • The result of this flow should always be that the CrazyGames account is linked to a (new or existing) in-game account.

The above cases are also illustrated in the diagram below. Please be sure you consult both the diagram and the cases, to have a complete implementation.

graph TB
GAME[Game starts] --> CHECKUSER{Get CG\nUser};
CHECKUSER -->|Logged out| SHOWAUTHPROMPT{Show CG auth\nprompt};
CHECKUSER -->|Logged in| USERLOGGEDIN{User is logged\nin CrazyGames};
USERLOGGEDIN --> |User logged in game,\n game acc linked to CG| STARTPLAYING[Start playing]
USERLOGGEDIN --> |User logged in game,\n not linked to CG| PROMPTLINK[Ask user to\nlink account]
USERLOGGEDIN --> |User not logged in game,\n but has game acc linked to CG| LOADGAMEACC[Log into game account]
USERLOGGEDIN --> |User not registered in game| CREATEGAMEACC[Create game acc\n or redirect to log in page]
SHOWAUTHPROMPT --> |User canceled| PLAYASGUEST[Play as guest\nif game allows];

Game login page

If you allow the user to log out during the game, or start the game as guest

  • You should add a CrazyGames Login button in your login screen, which triggers the same flow as described above in "At game launch".
  • If a user logs in with a different login type (e.g. Google or username/password), you should trigger an Account link prompt after login.

The user module can be accessed like this:


Check availability


The user account functionality is not available on other domains that embed your CrazyGames game. Before using any user account features, you should always ensure that the user account system is available.

const available = window.CrazyGames.SDK.user.isUserAccountAvailable;
console.log("User account system available", available);

Get current user


You can retrieve the user currently logged in CrazyGames with the following method:

const user = await window.CrazyGames.SDK.user.getUser();
console.log("Get user result", user);

If the user is not logged in CrazyGames, the returned user will be null

The returned user object will look like this:

  "username": "SingingCheese.TLNU",
  "profilePictureUrl": ""

System info


System info can be retrieved like this:

const systemInfo = window.CrazyGames.SDK.user.systemInfo;
console.log("System info", systemInfo);

The response will look like this:

  "countryCode": "US",
  "device": {
    "type": "desktop" // possible values: "desktop", "tablet", "mobile"
  "os": {
    "name": "Windows",
    "version": "10"
  "browser": {
    "name": "Chrome",
    "version": ""

For browser and os, the format is the same as ua-parser-js.

Auth prompt


By calling this method, the log in or register popup will be displayed on CrazyGames. The user can log in their existing account, or create a new account. The method returns the user object.

try {
  const user = await window.CrazyGames.SDK.user.showAuthPrompt();
  console.log("Auth prompt result", user);
} catch (e) {
  console.log("Error:", e);

The following errors can be returned:

  • showAuthPromptInProgress - an auth prompt is already opened on the website
  • userAlreadySignedIn - the user is already logged in
  • userCancelled - the user closed the auth prompt without logging in or registering

Get user token


The user token contains the userId of the player that is currently logged in CrazyGames, as well as other useful information (username, profilePictureUrl, etc). You should send it to your server when required, and verify/decode it there to extract the userId. This is useful for linking the user accounts for example, where you can have a column "crazyGamesId" in your user table that will be populated with the user id from the token.

You can retrieve the user token with the following method:

try {
  const token = await window.CrazyGames.SDK.user.getUserToken();
  console.log("Get token result", token);
} catch (e) {
  console.log("Error:", e);

The token has a lifetime of 1 hour. The method will handle the token refresh. We recommend that you don't store the token, and always call this method when the token is required.

The following error codes can be returned:

  • userNotAuthenticated - the user is not logged in CrazyGames
  • unexpectedError

The returned token can be decoded for testing purposes on

The token payload will contain the following data:

  "userId": "UOuZBKgjwpY9k4TSBB2NPugbsHD3",
  "gameId": "20267",
  "username": "RustyCake.ZU9H",
  "profilePictureUrl": "",
  "iat": 1670328680,
  "exp": 1670332280

When you need to authenticate the requests with your server, you should send the token together with the requests.

The token can be verified with the public key hosted at this URL We recommend that you fetch the key every time you verify the token, since it may change. Alternatively, you can implement a caching mechanism, and re-fetch it when the token fails to decode due to a possible key change.

Here is a TypeScript example that will help you decode and verify the token:

import * as jwt from "jsonwebtoken";
import axios from "axios";

export interface CrazyTokenPayload {
  userId: string;
  gameId: string;
  username: string;
  profilePictureUrl: string;

export const DecodeCGToken = async (token: string): Promise<CrazyTokenPayload> => {
  let key = "";

  try {
    const resp = await axios.get("");
    key =["publicKey"];
  } catch (e) {
    console.error("Failed to fetch CrazyGames public key", e);

  if (!key) {
    throw new Error("Key is empty when decoding CrazyGames token");

  const payload = jwt.verify(token, key, { algorithms: ["RS256"] });
  return payload as CrazyTokenPayload;

Auth listeners


You can register user auth listeners that are triggered when the player logs in CrazyGames. A log out doesn't trigger the auth listeners, since the entire page is refreshed when the player logs out.

const listener = (user) => console.log("User changed", user);

// add listener

// remove listener

After detecting a login using the Auth Listener, if you use the CrazyGames account as an identifier you should fetch the user's progress from your back-end.

If you rely on the data module or automatic progress save, our system automatically reloads the game in case of a login.



If you are using Firebase, account linking shouldn't be done client side. This is a security risk since anyone can inject any user id in the SDK. To implement account linking correctly with Firebase, you should use Cloud Functions with Firestore or Real Time Database. Integration suggestion:

  • send the token obtained from the CrazyGames SDK to a cloud function
  • the cloud function should parse and verify the token, and then create a new document in the database linking the CrazyGames user id obtained from the token to your user id
  • the cloud function creates a custom Firebase token and returns it back, and you use it to authenticate in Firebase
  • for future requests, the cloud function will check if there is any document linking the CrazyGames user id to your user id, and return the custom firebase token

We will release a more comprehensive guide about Firebase later.


If you'd like to keep other sign in providers (Google or Facebook for example), you'll need to handle account linking between the CrazyGames account and the other providers. Check User linking page to find out more about user account linking.

For requesting the user's permission to link their CrazyGames account to the in-game account, please use the provided account link modal and avoid implementing it yourself. This provides the players with a standard modal, and also allows them to select the "Always link accounts" option (coming soon).

Account link modal

You can display the modal by calling the following method:

try {
  const response = await window.CrazyGames.SDK.user.showAccountLinkPrompt();
  console.log("Link account response", response);
} catch (e) {
  console.log("Error:", e);

The response object will be either { "response": "yes" } or { "response": "no" }

The following error codes can be returned:

  • showAccountLinkPromptInProgress - the link account modal is already displayed
  • userNotAuthenticated - the user is not logged in CrazyGames




When the SDK is in the local environment (on or localhost) it will return some hardcoded default values for the method calls in the user module.

You can customize the returned local values by appending these query parameters:

  • ?user_account_available=false will change the response from the isUserAccountAvailable method to false (it returns true by default).
  • ?show_auth_prompt_response= will change the response from the showAuthPrompt method. It accepts the following values: user1, user2, user_cancelled
  • ?link_account_response= will change the response from the showAccountLinkPrompt method. It accepts the following values: yes, no, logged_out
  • ?user_response= will change the response from the getUser method. It accepts the following values: user1, user2, logged_out
  • ?token_response= will change the response from the getUserToken method. It accepts the following values: user1, user2, expired_token (to return an expired token), logged_out

By default, getUser returns user1, getUserToken returns token for user1, showAccountLinkPrompt returns yes, showAuthPrompt returns user1, and isUserAccountAvailable returns true.

QA Tool

When previewing the game in the QA tool, you can customize the user module behavior with the following modal:

QA tool fake user modal