Magic numbers are the first bits of a file which uniquely identify the type of file. This makes programming easier because complicated file structures need not be searched in order to identify the file type.
For example, a jpeg file starts with ffd8 ffe0 0010 4a46 4946 0001 0101 0047 ......JFIF.....G ffd8 shows that it's a JPEG file, and ffe0 identify a JFIF type structure. There is an ascii encoding of "JFIF" which comes after a length code, but that is not necessary in order to identify the file. The first 4 bytes do that uniquely.
This gives an ongoing list of file-type magic numbers.
File type | Typical extension |
Hex digits xx = variable |
Ascii digits . = not an ascii char |
---|---|---|---|
Bitmap format | .bmp | 42 4d | BM |
FITS format | .fits | 53 49 4d 50 4c 45 | SIMPLE |
GIF format | .gif | 47 49 46 38 | GIF8 |
Graphics Kernel System | .gks | 47 4b 53 4d | GKSM |
IRIS rgb format | .rgb | 01 da | .. |
ITC (CMU WM) format | .itc | f1 00 40 bb | .... |
JPEG File Interchange Format | .jpg | ff d8 ff e0 | .... |
NIFF (Navy TIFF) | .nif | 49 49 4e 31 | IIN1 |
PM format | .pm | 56 49 45 57 | VIEW |
PNG format | .png | 89 50 4e 47 | .PNG |
Postscript format | .[e]ps | 25 21 | %! |
Sun Rasterfile | .ras | 59 a6 6a 95 | Y.j. |
Targa format | .tga | xx xx xx | ... |
TIFF format (Motorola - big endian) | .tif | 4d 4d 00 2a | MM.* |
TIFF format (Intel - little endian) | .tif | 49 49 2a 00 | II*. |
X11 Bitmap format | .xbm | xx xx | |
XCF Gimp file structure | .xcf | 67 69 6d 70 20 78 63 66 20 76 | gimp xcf |
Xfig format | .fig | 23 46 49 47 | #FIG |
XPM format | .xpm | 2f 2a 20 58 50 4d 20 2a 2f | /* XPM */ |
File type | Typical extension |
Hex digits xx = variable |
Ascii digits . = not an ascii char |
---|---|---|---|
Bzip | .bz | 42 5a | BZ |
Compress | .Z | 1f 9d | .. |
gzip format | .gz | 1f 8b | .. |
pkzip format | .zip | 50 4b 03 04 | PK.. |
File type | Typical extension |
Hex digits xx = variable |
Ascii digits . = not an ascii char |
---|---|---|---|
TAR (pre-POSIX) | .tar | xx xx | (a filename) |
TAR (POSIX) | .tar | 75 73 74 61 72 | ustar (offset by 257 bytes) |
File type | Typical extension |
Hex digits xx = variable |
Ascii digits . = not an ascii char |
---|---|---|---|
MS-DOS, OS/2 or MS Windows | 4d 5a | MZ | |
Unix elf | 7f 45 4c 46 | .ELF |
##Miscellaneous files
File type | Typical extension |
Hex digits xx = variable |
Ascii digits . = not an ascii char |
---|---|---|---|
pgp public ring | 99 00 | .. | |
pgp security ring | 95 01 | .. | |
pgp security ring | 95 00 | .. | |
pgp encrypted data | a6 00 | ¦. |
@BathriNathan Although PNG allows a wide range of header fields, the magic word .PNG always appears in the first four bytes. So everything is fine. GIF always starts with GIF87a or GIF89a, which have both GIF8 in common. Everything is fine. I don’t know much about TIFF, because it has many variants like Exif, sDCF, TIFF/EP, TIFF/IT an GeoTIFF and also may come with different byte orders in the header.