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Communicate with Iframe Widget

Cross-origin communication between an Appsmith app and an embedded Iframe widget can be achieved through sending messages. This page shows how to send messages between the Appsmith app and an embedded Iframe widget.


  • An Iframe widget configured to embed your app in Appsmith.

Send messages to Iframe widget

The Iframe widget serves as the communication bridge between Appsmith and the embedded app. To send messages from Appsmith to your embedded app follow these steps:

Send message from Appsmith to Iframe widget
Send message from Appsmith to Iframe widget
  • To send a message from Appsmith to an embedded app within an Iframe widget, use the global function postWindowMessage in your JS Object or configure a post message action for your widget in the Properties pane. For example, to send a message on the click of a button widget, select the Post message action for the onClick event, add the message details in the Message field, and set the Target as the name of the Iframe widget (Iframe1). Alternatively, use the postWindowMessage() by enabling the JS as shown below:

    //replace the "Message content" with your actual message.
    //Set the Target as an Iframe widget. Replace "Iframe1" with the name of the
    // Iframe widget, and "<Appsmith_hosted_url>" with the Appsmith domain
    postWindowMessage("Message content", 'Iframe1', "<Appsmith_hosted_url>");
  • To receive the messages, use the addEventListener() method of the window object that adds an event listener in your parent app.

    //add this code in your app that you've embedded in Appsmith using the Iframe widget
    const messageHandler = (event) => {
    //The message sent is available in the event object.
    if(event) {
    // Read the message by using the property
    const messageReceived =;
    //Add code to manipulate the received message

    //add the event listener to read the incoming message
    window.addEventListener('message', messageHandler);

    // Remember to unlisten to the event when it's no longer needed
    // For example, unlisten when you have successfully processed the message
    // window.removeEventListener('message', messageHandler);

    Read the received message using the property. Add or update the code in the addEventListener() method to process the received message. Moreover, it's crucial to unlisten to the messages when they are no longer needed by invoking the removeEventListener() method.

Send messages to Appsmith

The Iframe widget also helps in sending messages to Appsmith from your embedded app. To send messages from your embedded app follow these steps:

Send message from Iframe widget to Appsmith
Send message from Iframe widget to Appsmith
  • To send messages to Appsmith, use the postMessage() method of the window object. Add the below code snippet in your app to send a message:

    //add this code to your embedded app.
    //message is the content of the message that you want to send to Appsmith
    function sendMessage(message) {
    if(message) {
    //Send the message in postMessage
    //replace the "<Appsmith_hosted_url>" with your Appsmith domain
    window.parent.postMessage(message, "<Appsmith_hosted_url>");

    Call the sendMessage() function whenever you want to send a message. Alternatively, you can directly use window.parent.postMessage(message, "<Appsmith_hosted_url>") in your code.

  • For receiving the message at Appsmith, configure the onMessageReceived() event of the Iframe widget in the Properties pane and show an alert or execute query by passing the received message. Read the received message using the message property of the Iframe widget (Iframe1) as shown below:

    //Iframe1 is the name of the Iframe widget.
    //replace it with the name of your Iframe widget

You may also choose to execute actions by adding callbacks to the onMessageReceived event, like showing a success or a failure message.

See also