# Hexadecimal RGB (HEX)

HEX is a variant of RGB in which the values for each parameter are in hexadecimal format. The syntax consists of a hash sign (`#`) followed by the hexadecimal values which will range from `00` (0 in decimal) to `FF` (255 in decimal):

[![Hexadecimal syntax: hash R R G G B B](https://cdn.hashnode.com/res/hashnode/image/upload/v1639796533223/_8Q9yjViI.png)](https://dev-to-uploads.s3.amazonaws.com/i/gsytxjq2m6d6h0n1ibjb.png)

In the past, there were only 3 hexadecimal parameters: one for red, another for green, and another for blue. A value of `00` would mean the complete absence of the color, while `FF` would indicate its complete presence. The higher the numbers, the lighter the color.

A fourth optional hexadecimal value can be provided to indicate alpha: `00` would be completely transparent, and `FF` completely opaque:  

    color: #FFFFFF;   /* white */
    color: #000000;   /* black */
    color: #FF0000;   /* red */
    color: #00FF00;   /* bright green (lime, see named colors below) */
    color: #0000ff;   /* blue */
    color: #800000;   /* darker red */
    color: #FF0000FF; /* red (opaque red) */
    color: #FF000088; /* semitransparent red */
    color: #FF000000; /* transparent (transparent red) */
    

Notice that CSS doesn't distinguish between upper- and lower-case for hexadecimal values, so you could write: `#ff0000` or `#FF0000` or `#Ff0000` and they would all be the same. Just keep it consistent to have a cleaner, more maintainable code.

If each of the color parameters –and transparency, if present– has the same digits (e.g. `#EE44FF`), there is the possibility to use a shorthand version of the hexadecimal notation, just putting each digit once:  

    /* regular hex */
    color: #336699;
    color: #336699FF;
    
    /* shorthand hex */
    color: #369;
    color: #369F;
    

This shorthand notation can only be used with a "small" subset of the colors: 4,096 of the 16,777,216 possible combinations (or 65,536 of the possible 4,294,967,296 combinations if we take into account alpha.)

Taking into consideration all the possible combinations, in the "best-case scenario", a color could be represented in up to 4 different ways with HEX:  

    color: #336699;
    color: #369;
    color: #336699FF;
    color: #369F;
    

All the browsers that were tested for this article supported all the notations of HEX listed above... Except for Edge on Windows that only supported HEX values without the alpha.