The open property of the HTMLDialogElement interface is a boolean value reflecting the open HTML attribute, indicating whether the <dialog> is available for interaction.


A boolean value representing the state of the open HTML attribute. true means it is set, and therefore the dialog is shown. false means it not set, and therefore the dialog is not shown.

The property is now read only — it is possible to set the value to programmatically show or hide the dialog.


The following example shows a simple button that, when clicked, opens a <dialog> containing a form via the showModal() method. From there you can click the Cancel button to close the dialog (via the HTMLDialogElement.close() method), or submit the form via the submit button.

<!-- Simple pop-up dialog box, containing a form -->
<dialog id="favDialog">
  <form method="dialog">
        <label for="favAnimal">Favorite animal:</label>
        <select id="favAnimal" name="favAnimal">
          <option>Brine shrimp</option>
          <option>Red panda</option>
          <option>Spider monkey</option>
      <button id="cancel" type="reset">Cancel</button>
      <button type="submit">Confirm</button>

  <button id="updateDetails">Update details</button>

  (() => {
    const updateButton = document.getElementById("updateDetails");
    const cancelButton = document.getElementById("cancel");
    const dialog = document.getElementById("favDialog");
    dialog.returnValue = "favAnimal";

    function openCheck(dialog) {
      if ( {
        console.log("Dialog open");
      } else {
        console.log("Dialog closed");

    // Update button opens a modal dialog
    updateButton.addEventListener("click", () => {

    // Form cancel button closes the dialog box
    cancelButton.addEventListener("click", () => {

Note: You can find this example on GitHub as htmldialogelement-basic (see it live also).


HTML Standard
# dom-dialog-open

Browser compatibility

BCD tables only load in the browser

See also

  • The HTML element implementing this interface: <dialog>.