The Windows Font Cache service caches data locally to the Local Service Profile in Server 2008 and above. The full path of the location is :
Over time these files which are name FontCache-S* take up quite a bit of space. Especially on RDS \ Citrix Xenapp Servers.
It would seem there is no maintenance built into Windows to clear these files that are left over. However they can be safely deleted.
If you try and delete the files straight away then you will find that some are locked by the service. To purge the files, I created a batch file that stops the service, starts it back up and then clears the relevant files.
net stop FontCache net start FontCache forfiles /P C:\Windows\ServiceProfiles\LocalService\AppData\Local /M ~FontCache* /D -1 /C "cmd /c del @path" forfiles /P C:\Windows\ServiceProfiles\LocalService\AppData\Local /M FontCache* /D -1 /C "cmd /c del @path"
Source : Microsoft Technet