⎗ application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

File Extensions

xlsx

Magic Bytes

1. ZIP file header

   Offset	0	1	2	3
   Byte	0x50	0x4b	0x03	0x04
   Char	P	K

References

• Media Type Assignment
• ECMA-376 - OOXML
• LOC Digital Formats - XLSX