File Extension SYD File Format Backup of startup files (QEMM) SYD stands for Backup of startup files (QEMM). 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 Mistakes That Startups Make #1: Timing Swedish bank Sparbanken Syd expands IT outsourcing to trading What's a good backup solution for home programmers?