Enable side loading

You may reach the bug “Sideloading of apps is not enabled on this site.” while deploying SharePoint addin to SharePoint Online. Run this powershell script then you will fix it. Make sure you have SharePoint Online Management Shell before you run it.

$programFiles = [environment]::getfolderpath("programfiles")

add-type -Path $programFiles'\SharePoint Online Management Shell\Microsoft.Online.SharePoint.PowerShell\Microsoft.SharePoint.Client.dll'

Write-Host 'To enable SharePoint app sideLoading, enter Site Url, username and password'
 
$siteurl = Read-Host 'Site Url'
$username = Read-Host "User Name"
$password = Read-Host -AsSecureString 'Password'
 

$outfilepath = $siteurl -replace ':', '_' -replace '/', '_'
 
try
{
    [Microsoft.SharePoint.Client.ClientContext]$cc = New-Object Microsoft.SharePoint.Client.ClientContext($siteurl)
 
    [Microsoft.SharePoint.Client.SharePointOnlineCredentials]$spocreds = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($username, $password)
 
    $cc.Credentials = $spocreds
    $sideLoadingEnabled = [Microsoft.SharePoint.Client.appcatalog]::IsAppSideloadingEnabled($cc);
    
    $cc.ExecuteQuery()
    
    if($sideLoadingEnabled.value -eq $false) {
        Write-Host -ForegroundColor Yellow 'SideLoading feature is not enabled on the site:' $siteurl
        $site = $cc.Site;
            $sideLoadingGuid = new-object System.Guid "AE3A1339-61F5-4f8f-81A7-ABD2DA956A7D"
            $site.Features.Add($sideLoadingGuid, $false, [Microsoft.SharePoint.Client.FeatureDefinitionScope]::None);
            $cc.ExecuteQuery();
           Write-Host -ForegroundColor Green 'SideLoading feature enabled on site' $siteurl
    }
    
    Else {
        Write-Host -ForegroundColor Green 'SideLoading feature is already enabled on site' $siteurl
    }
}
 
Catch { 
    Write-Host -ForegroundColor Red 'Error encountered when trying to enable SideLoading feature' $siteurl, ':' $Error[0].ToString();
}

After the powershell script is successfully run, you will see the SideLoading feature in enabled to your site.