File Extension NDX File Format Index file (Cindex) NDX stands for Index file (Cindex). 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 SQL Server error message 'Could not find the index entry for RID '1628000000a412030044160000869a0000040000' in the database What is difference between Clustered Index and Non-Cluster Index? How do search engines index image files?