File Extension T3X File Format TYPO3 Compressed Extension T3X stands for TYPO3 Compressed Extension. 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 Data deduplication and compression What is the range an image can be compressed? How can I access a .jls file or its bitstream compressed using JPEG-LS so that I may further compress it?