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Do not use. Use <dialog> or a popup window instead. Halts the script execution, creates a popup window, passes it parameters and returns a value when the new window is closed.

Method of dom/Windowdom/Window


var returnValue = window.showModalDialog(url, argumentsToPass, windowOptions);




String that specifies the URL of the document to load and display.



The arguments to use when displaying the new document. Use this parameter to pass a value of any type, including an array of values. The dialog box can extract the values passed by the caller from the dialogArguments property.



Specifies the window ornaments for the dialog box, using one or more of the following semicolon-delimited values:

Return Value

Returns an object of type anyany

The value of the returnValue property as set by the window of the document specified in url.


This example uses the showModalDialog method to open a customized dialog box.

<script type="text/javascript">
function fnRandom(iModifier){
   return parseInt(Math.random()*iModifier);
function fnSetValues(){
   var iHeight=oForm.oHeight.options[
   var sFeatures="dialogHeight: " + iHeight + "px;";
   return sFeatures;
function fnOpen(){
   var sFeatures=fnSetValues();
   window.showModalDialog("showModalDialog_target.htm", "",
<form name="oForm">
    Dialog Height
  <select name="oHeight">
    <option>-- Random --</option>
    Create Modal Dialog Box
  <input type="button" value="Push To Create" onclick="fnOpen()">

View live example


 Do not use. This API is being phased out. Chrome and Opera have already removed it by default and Firefox also considers following suit.


A modal dialog box retains the input focus while open. The user cannot switch windows until the dialog box is closed. Because a modal dialog box can include a URL to a resource in a different domain, do not pass information through the varArgIn parameter that the user might consider private. The varArgIn parameter can be referenced within the modal dialog box using the dialogArguments property of the window object. If the varArgIn parameter is defined as a string, the maximum string length that can be passed to the modal dialog box is 4096 characters; longer strings are truncated. You can set the default font settings the same way you set Cascading Style Sheets (CSS) attributes (for example, "font:3;font-size:4"). To define multiple font values, use multiple font attributes. To override center, even though the default for center is yes, you can specify either dialogLeft and/or dialogTop. When Windows Internet Explorer opens a window from a modal or modeless HTML dialog box by using the showModalDialog method or by using the showModelessDialog method, Internet Explorer uses Component Object Model (COM) to create a new instance of the window. Typically, the window is opened by using the first instance of an existing Internet Explorer process. When Internet Explorer opens the window in a new process, all the memory cookies are no longer available, including the session ID. This process is different from the process that Windows Internet Explorer uses to open a new window by using the open method. For Windows Internet Explorer 7, dialogHeight and dialogWidth return the height and width of the content area and no longer includes the height and width of the frame. Internet Explorer 7. Although a user can manually adjust the height of a dialog box to a smaller value —provided the dialog box is resizable— the minimum dialogHeight you can specify is 100 pixels, and the minimum dialogWidth you can define is 250 pixels. In versions earlier than Internet Explorer 7 the minimum value of the dialogWidth that can be specified is 100 pixels.

Note For Internet Explorer 7, help is not a valid value for sFeatures. In previous versions, help:{ yes | no | 1 | 0 | on | off } specified whether the dialog window displays the context-sensitive Help icon. This method must use a user-initiated action, such as clicking on a link or tabbing to a link and pressing enter, to open a pop-up window. The Pop-up Blocker feature in Microsoft Internet Explorer 6 blocks windows that are opened without being initiated by the user. Microsoft Internet Explorer 5 and later allows further control over modal dialog boxes through the status and resizable values in the varOptions parameter of the showModalDialog method. Turn off the status bar by calling the dialog box from a trusted application, such as Microsoft Visual Basic or an HTML Application (HTA), or from a trusted window, such as a trusted modal dialog box. These applications are considered to be trusted because they use Internet Explorer interfaces instead of the browser. Any dialog box generated from a trusted source has the status bar turned off by default. Resizing is turned off by default, but you can turn it on by specifying resizable=yes in the varOptions string of the showModalDialog method. The default unit of measure for dialogHeight and dialogWidth in Internet Explorer 5 and later is the pixel. The value can be an integer or floating-point number, followed by an absolute units designator (cm, mm, in, pt, or pc) or a relative units designator (em, ex, or px). For consistent results, specify the dialogHeight and dialogWidth in pixels when designing modal dialog boxes. As of Microsoft Internet Explorer 4.0, you can eliminate scroll bars on dialog boxes. To turn off the scroll bar, set the SCROLL attribute to false in the body element for the dialog window, or call the modal dialog box from a trusted application.