<script> tag in the
<head> tag of the page.
This API model uses promises and allows you to specify multiple operations in each request you send to the Office application. Batching operations in this manner can significantly improve add-in performance in Office applications on the web. Application-specific APIs were introduced with Office 2016 and cannot be used to interact with Office 2013.
There is also an application-specific API for Visio, but you can use it only in SharePoint Online pages to interact with Visio diagrams that have been embedded in the page. Office web add-ins are not supported in Visio.
See Using the application-specific API model to learn more about this API model .
Some Excel custom functions run within a unique runtime that prioritizes execution of calculations and don't have a task pane. These functions use a slightly different programming model and are called UI-less functions.
API requirement sets
Requirement sets are named groups of API members. Requirement sets can be specific to Office applications, such as the
ExcelApi 1.7 requirement set (a set of APIs that can only be used in Excel), or common to multiple applications, such as the
DialogApi 1.1 requirement set (a set of APIs that can be used in any Office application that supports the Dialog API).
Your add-in can use requirement sets to determine whether the Office application supports the API members that it needs to use. For more information about this, see Specify Office applications and API requirements.
Requirement set support varies by Office application, version, and platform. For detailed information about the platforms, requirement sets, and Common APIs that each Office application supports, see Office client application and platform availability for Office Add-ins.
If you plan to publish your add-in to AppSource and make it available within the Office experience, make sure that you conform to the Commercial marketplace certification policies. For example, to pass validation, your add-in must work across all platforms that support the methods that you define (for more information, see section 1120.3 and the Office Add-in application and availability page).