If you are developing a SharePoint hosted add-in or provider hosted add-in using visual studio 2015 or visual studio 2017, you may get the below error:
Error occurred in deployment step ‘Install App for SharePoint’: Sideloading of apps is not enabled on this site
The error looks like below while deploying SharePoint Add-in.
This error comes because of the URL we provide while developing an add-in in SharePoint. SharePoint App sideloading feature allows developer to install a SharePoint app directly into a site to explicitly bypass the regular governance controls of SharePoint.
Microsoft provides a new type of site, know as Developer site (Created by using Developer site template) to work with app development. These sites are specially designed for SharePoint Add-in developers to install and test apps before they are released to the store or app catalog or add-in catalog.
So the solution to this error is to create a developer site and use the developer site to create your SharePoint hosted add-in or provider hosted add-in. You can read steps to create a developer site in SharePoint online Office 365.