How can I blacklist filetypes from Spotlight search results?
Find the importer used to import that type of file.

mdimport -d 4 -n /path/to/file 2>&amp;1 | grep Imported



mdimport -d 4 -n ~/Desktop/avatar.png 2&gt;&amp;1 | grep Imported
2014-06-19 11:17:04.929 mdimport[30911:412893] Imported '/Users/grgarside/Desktop/avatar.png' of type 'public.png' with plugIn /System/Library/Spotlight/Image.mdimporter.


The above example shows the type as public.png in the Image.mdimporter importer.
Open /path/to/importer/Contents/Info.plist in an editor.
Find the item of the same type as the type of the file that you found from the above command and delete it.


Reimport the importer.

mdimport -r /path/to/importer



mdimport -r /System/Library/Spotlight/Image.mdimporter



Don't forget to have backups and note this procedure may be overridden on OS X updates.