Mozilla Archive (MAR) is a format used for transmitting updates to Mozilla software such as Firefox. (Not to be confused with MAFF, the Mozilla Archive Format for archiving copies of websites.) It consists of a series of files with some header information preceding them. No compression is done as part of this format, though the Mozilla update files which are sent in this manner are already in bzip2-compressed format. The files themselves are diff files generated with a variant of bsdiff.