diff --git a/src/enums/events.ts b/src/enums/events.ts
index f99afd5..79ff369 100644
--- a/src/enums/events.ts
+++ b/src/enums/events.ts
@@ -1,5 +1,8 @@
 export enum Events {
   ALL = '*',
+  // Topper
   ORDER_PLACED = 'orderPlaced',
-  WIDGET_CONTINUE_BUTTON_CLICKED = 'widgetContinueButtonClicked'
+  WIDGET_CONTINUE_BUTTON_CLICKED = 'widgetContinueButtonClicked',
+  // Internal
+  RESOLVE_HANDLER = 'resolveHandler'
 }
diff --git a/src/enums/handlers.ts b/src/enums/handlers.ts
new file mode 100644
index 0000000..c1311f7
--- /dev/null
+++ b/src/enums/handlers.ts
@@ -0,0 +1,3 @@
+export enum Handlers {
+  ASSETS = 'assets'
+}
diff --git a/src/enums/index.ts b/src/enums/index.ts
index c2c138d..ab4e9c3 100644
--- a/src/enums/index.ts
+++ b/src/enums/index.ts
@@ -1,4 +1,6 @@
 export * from './environments';
 export * from './events';
+export * from './handlers';
+export * from './sources';
 export * from './urls';
 export * from './variants';
diff --git a/src/enums/sources.ts b/src/enums/sources.ts
new file mode 100644
index 0000000..140a7c6
--- /dev/null
+++ b/src/enums/sources.ts
@@ -0,0 +1,4 @@
+export enum Sources {
+  EVENT = '@topper-web-sdk-event',
+  HANDLER = '@topper-web-sdk-handler'
+}
diff --git a/src/interfaces/config.ts b/src/interfaces/config.ts
index 244d160..06ec00d 100644
--- a/src/interfaces/config.ts
+++ b/src/interfaces/config.ts
@@ -5,6 +5,7 @@ export interface Config {
   environment?: Environments;
   is_android_app?: boolean;
   is_ios_app?: boolean;
-  variant?: Variants;
   theme?: string;
+  use_assets?: boolean;
+  variant?: Variants;
 }
diff --git a/src/topper-web-sdk.ts b/src/topper-web-sdk.ts
index d26c169..b8ea3ea 100644
--- a/src/topper-web-sdk.ts
+++ b/src/topper-web-sdk.ts
@@ -1,12 +1,12 @@
 import { Config } from './interfaces';
-import { Environments, Events, Urls, Variants } from './enums';
-import { EventHandler } from 'types';
+import { Environments, Events, Handlers, Sources, Urls, Variants } from './enums';
+import { EventHandler, Handler } from 'types';
+import isPromise from 'utils/isPromise';
 import queryString from 'query-string';
 
-const TOPPER_WEB_SDK_EVENT_SOURCE = '@topper-web-sdk';
-
 class TopperWebSdk {
   private eventHandlers: { [key in Events]?: EventHandler[] } = {};
+  private handlers: { [key in Handlers]?: Handler } = {};
   private handleMessage: ((event: MessageEvent) => void) | null = null;
   private isInitialized: boolean = false;
   private targetWindow: Window | null = null;
@@ -18,13 +18,39 @@ class TopperWebSdk {
       environment: Environments.PRODUCTION,
       is_android_app: false,
       is_ios_app: false,
+      use_assets: false,
       variant: Variants.NEW_TAB,
       ...config
     };
   }
 
+  static getMainWindow() {
+    return window.self !== window.top ? window.parent : window.opener;
+  }
+
+  static resolveHandler(handlerName: Handlers): Promise<void> {
+    const mainWindow = this.getMainWindow();
+
+    mainWindow.postMessage(
+      {
+        name: Events.RESOLVE_HANDLER,
+        payload: handlerName,
+        source: Sources.HANDLER
+      },
+      '*'
+    );
+
+    return new Promise(resolve => {
+      window.addEventListener('message', event => {
+        if (event.data.name === Events.RESOLVE_HANDLER && event.data.payload && event.data.source === Sources.HANDLER) {
+          resolve(event.data.payload);
+        }
+      });
+    });
+  }
+
   static triggerEvent(eventName: Events, data?: any): void {
-    const mainWindow = window.self !== window.top ? window.parent : window.opener;
+    const mainWindow = this.getMainWindow();
 
     if (!mainWindow) {
       return;
@@ -34,7 +60,7 @@ class TopperWebSdk {
       {
         name: eventName,
         payload: data,
-        source: TOPPER_WEB_SDK_EVENT_SOURCE
+        source: Sources.EVENT
       },
       '*'
     );
@@ -54,9 +80,13 @@ class TopperWebSdk {
         return;
       }
 
-      if (event.data && event.data.name && event.data.source === TOPPER_WEB_SDK_EVENT_SOURCE) {
+      if (event.data.name && event.data.source === Sources.EVENT) {
         this.triggerEvent(event.data.name as Events, event.data.payload);
       }
+
+      if (event.data.name === Events.RESOLVE_HANDLER && event.data.payload && event.data.source === Sources.HANDLER) {
+        this.resolveHandler(event.data.payload as Handlers);
+      }
     };
 
     window.addEventListener('message', this.handleMessage);
@@ -82,7 +112,8 @@ class TopperWebSdk {
       ...(isTopperSelfEmbed && { embed: 1 }),
       ...(this.config.theme && { theme: this.config.theme }),
       ...(this.config.is_android_app && { is_android_app: 1 }),
-      ...(this.config.is_ios_app && { is_ios_app: 1 })
+      ...(this.config.is_ios_app && { is_ios_app: 1 }),
+      ...(this.config.use_assets && { use_assets: 1 })
     };
 
     const url = queryString.stringifyUrl({ query: queryParams, url: `${baseUrl}/` });
@@ -112,6 +143,29 @@ class TopperWebSdk {
 
     this.eventHandlers[eventName]?.push(handler);
   }
+
+  registerHandler(handlerName: Handlers, handler: Handler): void {
+    if (!(typeof handler === 'function' || isPromise(handler))) {
+      throw new Error('Handler must be a Promise or an async function.');
+    }
+
+    this.handlers[handlerName] = handler;
+  }
+
+  async resolveHandler(handlerName: Handlers) {
+    const handler = this.handlers[handlerName];
+
+    const handlerResult = isPromise(handler) ? await handler : await handler?.();
+
+    this.targetWindow?.postMessage(
+      {
+        name: Events.RESOLVE_HANDLER,
+        payload: handlerResult,
+        source: Sources.HANDLER
+      },
+      '*'
+    );
+  }
 }
 
 export { TopperWebSdk };
diff --git a/src/types/handler.ts b/src/types/handler.ts
new file mode 100644
index 0000000..5cc47b9
--- /dev/null
+++ b/src/types/handler.ts
@@ -0,0 +1 @@
+export type Handler = () => Promise<void>;
diff --git a/src/types/index.ts b/src/types/index.ts
index a54ccf8..9d52f70 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -1 +1,2 @@
 export * from './event-handler';
+export * from './handler';
diff --git a/src/utils/isPromise.ts b/src/utils/isPromise.ts
new file mode 100644
index 0000000..b19ce4b
--- /dev/null
+++ b/src/utils/isPromise.ts
@@ -0,0 +1,7 @@
+const isObject = (value: any) => value !== null && (typeof value === 'object' || typeof value === 'function');
+
+const isPromise = (value: any) =>
+  value instanceof Promise ||
+  (isObject(value) && typeof value.then === 'function' && typeof value.catch === 'function');
+
+export default isPromise;