Magic numbers in files

Examples

Some examples:

* Compiled Java class files (bytecode) start with hex CAFEBABE. When compressed with Pack200 the bytes are changed to CAFED00D.
* GIF image files have the ASCII code for "GIF89a" (47 49 46 38 39 61) or "GIF87a" (47 49 46 38 37 61)
* JPEG image files begin with FF D8 and end with FF D9. JPEG/JFIF files contain the ASCII code for "JFIF" (4A 46 49 46) as a null terminated string. JPEG/Exif files contain the ASCII code for "Exif" (45 78 69 66) also as a null terminated string, followed by more metadata about the file.
* PNG image files begin with an 8-byte signature which identifies the file as a PNG file and allows detection of common file transfer problems: \211 P N G \r \n \032 \n (89 50 4E 47 0D 0A 1A 0A). That signature contains various newline characters to permit detecting unwarranted automated newline conversions, such as transferring the file using FTP with the ASCII transfer mode instead of the binary mode.
* Standard MIDI music files have the ASCII code for "MThd" (4D 54 68 64) followed by more metadata.
* Unix script files usually start with a shebang, "#!" (23 21) followed by the path to an interpreter.
* PostScript files and programs start with "%!" (25 21).
* PDF files start with "%PDF" (25 50 44 46).
* Old MS-DOS .exe files and the newer Microsoft Windows PE (Portable Executable) .exe files start with the ASCII string "MZ" (4D 5A), the initials of the designer of the file format, Mark Zbikowski. The definition allows "ZM" (5A 4D) as well but this is quite uncommon.
* The Berkeley Fast File System superblock format is identified as either 19 54 01 19 or 01 19 54 depending on version; both represent the birthday of the author, Marshall Kirk McKusick.
* The Master Boot Record of bootable storage devices on almost all IA-32 IBM PC Compatibles has a code of AA 55 as its last two bytes.
* Executables for the Game Boy and Game Boy Advance handheld video game systems have a 48-byte or 156-byte magic number, respectively, at a fixed spot in the header. This magic number encodes a bitmap of the Nintendo logo.
* Zip files begin with "PK" (50 4B), the initials of Phil Katz, author of DOS compression utility PKZIP.