Did you know there are 4 and 8 digit hex codes (#11223344?) for colours? 🤯

10 years as a developer and somehow I have missed that there are 4 digit (#1234) and 8 digit (#11223344) hex codes for colours⁉ Here is what I learned about what they are and how we use them!

Before we start though, a big shout out to @afif (the CSS guru!) who was the one who opened my eyes to this when discussing how to make an SVG "fade out" from one side to the other!

Prefer to consume content on Twitter?

Just as a very quick aside, if you prefer to read twitter threads rather than long form content then I have already created one about 4 and 8 digit hex codes here:

What do 8 digit Hexadecimal colour codes do?

In a nutshell they are similar to RGBA, essentially they let you add opacity with the last 2 characters.

So instead of:

#RRGGBB

As you would do in a normal 6 digit colour hex code you can do

#RRGGBBAA

and add an opacity value using the last 2 characters!

I have put together a quick demo showing this here where I use the same colour code (#336699) and then add bb to it to make it semi transparent (#336699bb):

With 8 digit colour hex codes there are a couple of "gotchyas"

Moving from a RGBA mindset to a 8 digit hex code system takes a tiny bit of getting used to!

The first 6 characters are just the same as they always are, but opacity is now on a scale of 0-255 ("00" to "ff")

So 00 still represents 0% opacity, but 255 (ff) now represents 100% opacity!

A few examples

Just to make it a bit more clear, here are a few examples:

Opacity 8 digit Hex Code equivalent explanation
0% #RRGGBB00 00 in hexadecimal is still 0
10% #RRGGBB1A 1A in hexadecimal is 26. 26 is ~10% of 255 (so 26/255 =~ 10%)
50% #RRGGBB80 1A in hexadecimal is 128. 128 is ~50% of 255 (so 128/255 =~ 50%)
90% #RRGGBBE6 E6 in hexadecimal is 230. 230 is ~90% of 255 (so 230/255 =~ 90%)
100% #RRGGBBFF FF in hexadecimal is 255. 255 is 100% of 255 (so 255/255 = 100%)

Hopefully it is becoming clearer now, but just in case...

A mini tool to help understand 8 digit hex codes!

This tool will hopefully help it sink in (if it hasn't already)

Explanation

Enter the original colour you want to work with, either using the colour picker, hex colour or RGB colour (I had an issue with HSL so I have disabled those inputs 😪).

Then move the opacity slider or enter an opacity value.

Below that you will see a section with your final colour code and the resulting colour displayed on a striped background (assuming you lower the opacity of course!)

Below that there is a further explanation about the hex code it generated. It will also tell you if you can use a 4 digit hex code (more on that after the demo!)

8 digit hex code demonstration!

Have a play, there isn't much error checking though so check you enter valid numbers or...🔥💻🚒 could be the result! 🤣

4 digit hexadecimal colour codes

If you played with the above example long enough you may have noticed that occasionally you get a valid 4 digit hex code in the "results" or "details" section.

So how the heck does that work?

The rules are quite simple:

R1 = R2
G1 = G2
B1 = B2
A1 = A2

If all of the above are true then you can turn your 8 digit hex code into the short hand 4 digit hex code by taking R1, G1, B1 and A1 and combining them!

4 digit hex code examples:

#22446688 ✅
This can be shortened as 2==2 and 4==4 and 6==6 and 8==8. It will become #2468
#22456688 ❌
This can't be shortened as our G1 and G2 are not the same (4!==5). You would have to use the full 8 digit hex code #22456688
#AA4488DD ✅
Yet again R1==R2 (A==A), G1==G2(4==4) etc. So this can be turned into a 4 digit hex code (#A48D)

Making it a bit easier!

Trying to remember that "BF" is 191 in decimal which is 75% of 255 is hard work!

So I created this super handy table with all of the codes in it (or you can use the hex opacity demo I linked earlier)

Opacity to hex code conversion table

You can skip this long table if you want, but it might be worth bookmarking this article so you can use it for reference!

Opacity Percent Equivalent on 0-255 scale) Hex Code
100% 255 FF
99% 252 FC
98% 250 FA
97% 247 F7
96% 245 F5
95% 242 F2
94% 240 F0
93% 237 ED
92% 235 EB
91% 232 E8
90% 230 E6
89% 227 E3
88% 224 E0
87% 222 DE
86% 219 DB
85% 217 D9
84% 214 D6
83% 212 D4
82% 209 D1
81% 207 CF
80% 204 CC
79% 201 C9
78% 199 C7
77% 196 C4
76% 194 C2
75% 191 BF
74% 189 BD
73% 186 BA
72% 184 B8
71% 181 B5
70% 179 B3
69% 176 B0
68% 173 AD
67% 171 AB
66% 168 A8
65% 166 A6
64% 163 A3
63% 161 A1
62% 158 9E
61% 156 9C
60% 153 99
59% 150 96
58% 148 94
57% 145 91
56% 143 8F
55% 140 8C
54% 138 8A
53% 135 87
52% 133 85
51% 130 82
50% 128 80
49% 125 7D
48% 122 7A
47% 120 78
46% 117 75
45% 115 73
44% 112 70
43% 110 6E
42% 107 6B
41% 105 69
40% 102 66
39% 99 63
38% 49 31
37% 94 5E
36% 92 5C
35% 89 59
34% 87 57
33% 84 54
32% 82 52
31% 79 4F
30% 77 4D
29% 74 4A
28% 71 47
27% 69 45
26% 66 42
25% 64 40
24% 61 3D
23% 59 3B
22% 56 38
21% 54 36
20% 51 33
19% 48 30
18% 46 2E
17% 43 2B
16% 41 29
15% 38 26
14% 36 24
13% 33 21
12% 31 1F
11% 28 1C
10% 26 1A
9% 23 17
8% 20 14
7% 18 12
6% 15 0F
5% 13 0D
4% 10 0A
3% 8 08
2% 5 05
1% 3 03
0% 0 00

Wrapping up on 8 digit hex codes!

So there you have it, a quick introduction to 4 and 8 digit hex codes!

If you want to read more about it the following resource might be useful: W3 CSS Color Module level 4

If you liked this article...

I hope you enjoyed this article.

If you did could you do me a quick favour and retweet the twitter thread I wrote about this?

It would really help me out and would be massively appreciated as I am trying to grow my tiny twitter following this year!

Thanks in advance and thank you for reading!

Final bit of silliness

Oh and because I didn't know this it is time to give back my developer card according to @alvaromontoro, always good to know you can rely on friends to support you! 🤣

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