Office.initialize event (JavaScript API for Office)

Office Add-ins

Occurs when the runtime environment is loaded and the app is ready to start interacting with the application and hosted document.

Last modified: June 22, 2015

Note Note

The name "apps for Office" is changing to "Office Add-ins". During the transition, the documentation and the UI of some Office host applications and Visual Studio tools might still use the term "apps for Office". For details, see New name for apps for Office and SharePoint.


Access, Excel, Outlook, PowerPoint, Project, Word

Last changed in


See all support details

Office.initialize = function (reason) {/* initialization code */}

The reason parameter of the initialize event listener function returns an InitializationReason enumeration value that specifies how initialization occurred. A task pane or content app can be initialized in two ways:

  • The user just inserted it from Recently Used Apps section of the App drop-down list on the Insert tab of the ribbon in the Office host application, or from Insert app dialog box.

  • The user opened a document that already contains the app.

Note Note

The reason parameter of the initialize event listener function only returns an InitializationReason enumeration value for task pane and content apps. It does not return a value for mail apps.

You can use the value of the InitializationEnumeration to implement different logic for when the app is first inserted versus when it is already part of the document. The following example shows some simple logic that uses the value of the reason parameter to display how the task pane or content app was initialized.

Office.initialize = function (reason) {
    // Checks for the DOM to load using the jQuery ready function.
    $(document).ready(function () {
    // After the DOM is loaded, app-specific code can run.
    // Display initialization reason.
    if (reason == "inserted")
    write("The app was just inserted.");

    if (reason == "documentOpened")
    write("The app is already part of the document.");

// Function that writes to a div with id='message' on the page.
function write(message){
    document.getElementById('message').innerText += message; 

A checkmark (√) in the following matrix indicates that this event is supported in the corresponding Office host application. An empty cell indicates that the Office host application doesn't support this event.

For more information about Office host application and server requirements, see Requirements for running apps for Office.

Office for Windows desktop

Office Online
(in browser)

Office for iPad

OWA for Devices

Outlook for Mac







Minimum permission level


App types

Content, mail, task pane








Added support for Excel and Word in Office for iPad.


Added support for initializing content apps for Access.



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