Most Recent Patch, July 2025 – 16.0.5508.1000
To see which build your farm is, go to Central Administration > System Settings > Manage servers in your farm (/_admin/FarmServers.aspx)
Or using Windows PowerShell: (get-spfarm).buildversion
Or the Registry: HKLM\SOFTWARE\Microsoft\Office Server\16.0\BuildVersion
To see which build your farm is at with Fiddler, open the site in question and view Inspectors > Headers and under Miscellaneous check the build under MicrosoftSharePointTeamServices header.
To see which build your products are, go to Central Administration > Upgrade and Migration > Check Product and patch installation status. (/_admin/PatchStatus.aspx)