Complex sentence: The whole UEF file, including the header, may optionally be compressed in gzip format; by examining the start of the file for a gzip or UEF header, a decompression library can be invoked as appropriate.
Split into simpler sentences: The whole UEF file, including the header, may optionally be compressed in gzip format. By examining the start of the file for a gzip or UEF header, a decompression library can be invoked as appropriate.