In this article you will learn about App Catalogue in SharePoint Online.
Introduction SharePoint App Catalog is the central location to publish our Apps and we can access the same across the site collection. App Catalog is nothing but a site collection scoped at Application level, we can have only one App Catalog in the web application. You create the App Catalog site collection from SharePoint Central Administration or from Admin site in Office 365/Online. Creating App Catalog In this example I am going to create an App Catalogue in SharePoint Online, and I will be publishing my custom app in that App Catalogue. Once it’s published I am going to use same in a different site collection within the Web Application. Steps to create App Catalog
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SharePoint Framework (SPFx) A Developers Guide