SharePoint Default Trusted file (MIME) types

Each Web Application in SharePoint 2010 and 2013 has an AllowedInlineDownloadedMimeTypes property within which a list of trusted file (MIME) types exists. Firstly, there is no “untrusted” list, only a “trusted” list. It is safe to assume that if a MIME type is not included in this list, it is untrusted by default and is subject to the “X-Download-Options: noopen” HTTP Response header. The most common example of this is PDF documents, MIME type “application/pdf”. 

In the SharePoint 2010 Management Shell, you can easily find out which types are trusted out of the box by executing the following PowerShell snippet:

Get-SPWebApplication "http://yourwebapplicationurl" | Foreach-Object {$_.AllowedInlineDownloadedMimeTypes}

You could also use the following snippet to achieve the same output: 

$webApplication = Get-SPWebApplication "http://yourwebapplicationurl"            

$webApplication.AllowedInlineDownloadedMimeTypes

Again, it is important to note that each web application has its own AllowedInlineDownloadedMimeTypes property. 

Force Browser to save office files locally

if you are stuck like me and trying to find a solution to force browsers to only save office documents (word and excel) locally and not try to open in browser follow the steps below:


$webApplication = Get-SPWebApplication "http://localhost"
$webApplication.AllowedInlineDownloadedMimeTypes.Remove("application/vnd.openxmlformats-officedocument.wordprocessingml.document")
$webApplication.AllowedInlineDownloadedMimeTypes.Remove("application/msword")
$webApplication.AllowedInlineDownloadedMimeTypes.Remove("application/vnd.ms-word.document.12")
$webApplication.AllowedInlineDownloadedMimeTypes.Remove("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
$webApplication.Update()