These software let you open, view, and edit Hexadecimal files that normal text editor software can't do.
HxD Hex Editor
HxD Hex Editor is a freeware to edit HEX files. It is a simple hex editor and lets you edit multiple hex files simultaneously. It can also edit Decimal files and octal files.
Free Hex Editor Neo
Free Hex Editor Neo is another free hex file editor freeware. It can also edit decimal, ASCII, double, binary, and float and open multiple files simultaneously in different tabs.
WinVi
WinVi is an open source hex editor software. It is a simple freeware to open, view, and edit different types of files such as: Hex, ASCII, DOS, EBCDIC, UTF-8, and UTF-16.
BitEdit9
BitEdit9 is a Hex viewer, Hex Editor, Decimal Editor, Decimal Viewer, Binary Viewer, Binary Editor, Octal Viewer, and Octal Editor.
Hextreme Hex Editor
Hextreme Hex Editor can open multiple hex files simultaneously in different tabs. You can search any hex code, go to any desired address line, and go to decimal place.
wxHexEditor
wxHexEditor supports multiple tabs, so that you can easily open and edit multiple hex files at a time.