Content Type Hub in SharePoint Online
Standards are good and sometimes you want some standards in SharePoint Online. A useful tool is the Content Type Hub. You should know it from SharePoint 2010 and 2013. Whenever you need it, you can create one, by activating the Site Collection Feature "Content Type Syndication Hub". This feature allows you to publish your Site Columns and Site Content Types to every other site Collection. So you might thing you can build your hub in SharePoint Online by activating the feature on a new Site Collection. If you do so you will get an error. It tells your proxy is not working correctly, but this is not true. In fact there is already an hub and you cannot build a second one. The hub is hidden so you cannot see it in the Site Collection Overview in your admin center. You need to know the URL: https://yourprefix.sharepoint.com /sites/contenttypehub