File Extension _DL File Format Compressed dll file _DL stands for Compressed dll file. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Run.DLL Work of .DLL and .API files What app opens a .DLL file?