In terms of backwards compatibility, SharePoint 2013 provides great support allowing you not only to run SharePoint 2010 migrated sites without switching to a SharePoint 2013 mode, but also to create site collections in two possible user experiences: SharePoint 2010 and SharePoint 2013.
Fortunately, this default behavior available when creating a new site collection can be easily changed at the web application level by using the server-side object model or Windows PowerShell:
First, you need to access SharePoint 2013 in a CloudShare environment and start the SharePoint 2013 Management Shell. Once the Shell is ready, just execute the following PowerShell cmdlets:
$wa.CompatibilityRange = [Microsoft.SharePoint.SPCompatibilityRange]::NewVersion
As you can see in the output Windows, the compatibility level for the web application is now 15 so it’s not possible to create new site collections in a SharePoint 2010 mode as before. Initially we had a 14 minimum value and 15 maximum value for the compatibility level. We change both values to 15 by means of the CompatibilityRange property that can take three different values:
NewVersion: only SharePoint 2013 mode.
OldVersion: only SharePoint 2010 mode.
AllVersions: both modes, this is the default value for each Web Application in SharePoint 2013.
Finally, if you try to create a new site collection under the modified web application you will see that there is no option for choosing between a SharePoint 2010 mode or a SharePoint 2013 mode once. The site collection will be created in the 2013 experience version.
And that’s all about how to change the SharePoint 2013 compatibility range at the web application level. Happy CloudSharing J.