Uxn program file
From Just Solve the File Format Problem
Uxn is a simple virtual machine. A Uxn program file is loaded into the virtual machine's memory starting at address 0x0100, and then execution starts at address 0x0100.
Identification
Any valid uxn file will have the first byte being a nonzero multiple of thirty-two, other than thirty-two itself.
A uxn file with metadata will have A0 xx xx 80 06 37
as the first six bytes, where the second and third bytes are a big-endian 16-bit address of the metadata (where the beginning of the file is address 0x0100).