In this blog, you will see how to get all the file types from SharePoint 2013 Enterprise Search using Powershell.
Navigate to Central Administration=> Application Management=> Manage service applications => Search Service Application=> File Types (under Crawling section in the left navigation). You should be able to see all the file types that are included in the content index.
Powershell Script:
## Get the Enterprise Search Service Application
$ssa = Get-SPEnterpriseSearchServiceApplication
## Get all the file formats available for the Enterprise Search
$fileFormatColl=Get-SPEnterpriseSearchFileFormat –SearchApplication $ssa
## Loop through each file format
foreach($fileFormat in $fileFormatColl)
{
## Display the file name extension
write-host -f Green $fileFormat.Identity
}