Preon is described as 'aims to provide a framework for dealing with binary encoded data; or more specifically, it aims to deal with situations in which bytes are considered to be overkill'. There are eight alternatives to Preon for Windows, Linux and Mac. The best alternative is HxD, which is free. Other great apps like Preon are 010 Editor (Paid), WinHex (Paid), Synalyze It! (Paid) and Kaitai Struct (Free, Open Source).
010 Editor is a professional text/hex editor designed to edit any file, drive, or process on your machine. Using Binary Templates technology, 010 Editor allows a binary file to be parsed into a data structure that can be understood.
WinHex is a hexadecimal editor capable of opening disks, sectors, files (native support for FAT, NTFS, Ext2/3, ReiserFS, Reiser4, UFS, CDFS, UDF) and physical memory (RAM). It can read, write and extract data for a further forensic analysis.
DHEX is a more than just another hex editor: It includes a diff mode, which can be used to easily and conveniently compare two binary files. Since it is based on ncurses and is themeable, it can run on any number of systems and scenarios.