Disable modern experience for a site collection

Question

Is there a way to disable the modern experience for the site collection and not all of SharePoint? I googled and saw where to disable the Modern and switch back to Classic at the admin level, but I don't want this for all of SharePoint. I don't want to completely miss out on all of the new things coming.

Answer 1

It is possible to do at the site collection level or at the web level, it is only settable by CSOM/PowerShell. This is how we manage it in our PowerShell module for working with SharePoint Online.

function Set-NewExperience{
    <#
    .Synopsis
       Sets the document library experience for a site or web
    .DESCRIPTION
       Sets the document library experience for a site or web
    .EXAMPLE
       The following would disable the new experience for an entire site collection
       Set-NewExperience -Url "https://tenant.sharepoint.com/teams/eric" -Scope Site -State Disabled
    .EXAMPLE
       The following would disable the new experience for a single web
       Set-NewExperience -Url "https://tenant.sharepoint.com/teams/eric" -Scope Web -State Disabled
    .EXAMPLE
       The following would enable the new experience for an entire site collection
       Set-NewExperience -Url "https://tenant.sharepoint.com/teams/eric" -Scope Site -State Enabled
    .Link
    https://support.office.com/en-us/article/Switch-the-default-for-document-libraries-from-new-or-classic-66dac24b-4177-4775-bf50-3d267318caa9
    #>
    Param
    (
        [Parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)]
        [string]$Url,
        [Parameter(Mandatory=$true)][ValidateSet("Site", "Web")]
        [string]$Scope,
        [Parameter(Mandatory=$true)][ValidateSet("Enabled", "Disabled")]
        [string]$State

    )

    Begin{
        $context = New-Object Microsoft.SharePoint.Client.ClientContext($Url)
        $context.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($credential.UserName, $credential.Password)
    }
    Process{

        if($Scope -eq "Site"){
            # To apply the script to the site collection level, uncomment the next two lines.
            $site = $context.Site
            $featureguid = new-object System.Guid "E3540C7D-6BEA-403C-A224-1A12EAFEE4C4"
        }
        else{
            # To apply the script to the website level, uncomment the next two lines, and comment the preceding two lines.
            $site = $context.Web
            $featureguid = new-object System.Guid "52E14B6F-B1BB-4969-B89B-C4FAA56745EF" 
        }
        if($State -eq "Disabled")
        {
            # To disable the option to use the new UI, uncomment the next line.
            $site.Features.Add($featureguid, $true, [Microsoft.SharePoint.Client.FeatureDefinitionScope]::None)
            $message = "New library experience has been disabled on $URL"
        }
        else{
            # To re-enable the option to use the new UI after having first disabled it, uncomment the next line.
            # and comment the preceding line.
            $site.Features.Remove($featureguid, $true)
            $message = "New library experience has been enabled on $URL"
        }
        try{
            $context.ExecuteQuery()
            write-host -ForegroundColor Green $message
        }
        catch{
            Write-Host -ForegroundColor Red $_.Exception.Message
        }
    }
    End{
        $context.Dispose()    
    }
}

Answer 2

You can now set this for individual lists and libraries by going to list/library settings > Advanced Settings > List Experience.

https://support.office.com/en-us/article/switch-the-default-experience-for-lists-or-document-libraries-from-new-or-classic-66dac24b-4177-4775-bf50-3d267318caa9