Hexadecimal

Hexadecimal is a base-16 positional number system that uses sixteen symbols: 0–9 for values zero to nine and A–F for ten to fifteen. It's widely used in computing because each hex digit maps neatly to four binary bits, making it a compact way to write binary data — memory addresses, byte values, and CSS colors (e.g. #1f6feb) are all written in hex.

Example: Hex FF = 255 in decimal = 11111111 in binary.