First we need to understand what a Site Definition is and why we are resetting the option. A Site Definition is the core definition of what a site is in SharePoint.
Reference: MSDN

Procedure: Site Settings >> Site Actions>> Reset to Site Definition



Reset to Site Definition removes any customizations and reverts the file back to the version originally deployed via the Site Definition. Customized pages are stored in the Content Database (a copy with changes) and are called unghosted. When you reset, the customized copy is deleted and the version on the file system (the Site Definition version) is used.



Enter the Local Site URL and you will get Pop-up notification.



If you select another Check box option in this page then you will get the following popup.



Reset the Site Definition using PowerShell Script: Entire siteCollection
  1. $SiteURL ="https://gauti.sharepoint.com"
  2. $web = Get-SPWeb $SiteURL
  4. #Revert all webs to Site Definition
  5. Get-SPSite $SiteURL | Get-SPWeb | foreach-object {
  6. $_.RevertAllDocumentContentStreams()
  7. Write-Debug "Site Resetted: $($web.Url)"
  8. }
  10. Specific list/Site
  11. Add-PSSnapin microsoft.sharepoint.powershell -ErrorAction SilentlyContinue
  13. $WebURL ="https://gauti.sharepoint.com/sites/apps"
  15. $web = Get-SPWeb $SiteURL
  16. $web.RevertAllDocumentContentStreams();
  17. $web.Update()
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