File Extension _DL File Format Form of DLL File _DL stands for Form of 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 Entry Point not Found Exception C# multi instances of the form and subform Access 2003 IIF Function?