What is the difference between 3-digit and 6-digit hex colors?

A 3-digit color like #RGB is shorthand where each digit is doubled, so #ABC expands to #AABBCC. Both represent the same 256³ color space with less precision.

How do I match hex colors with alpha channel?

Add a third alternation for 8-digit hex: #?([a-fA-F0-9]{8}|[a-fA-F0-9]{6}|[a-fA-F0-9]{3}). The last two digits represent the alpha channel.

How do I extract all hex colors from a CSS file?

Use the global flag /g and a pattern with word boundaries to find all hex colors in a block of CSS text. The tester shows all matches highlighted in the input.

Regex Pattern for Hex Colors

Hex color codes appear in CSS, design tokens, and configuration files. This example matches both shorthand 3-digit (#RGB) and full 6-digit (#RRGGBB) formats with an optional leading hash. The tester helps you verify edge cases like uppercase letters and missing hashes. Extend the pattern to support 8-digit hex with alpha channel (#RRGGBBAA) if your use case requires it.

Example

/^#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$/

# Test cases:
#FF5733
#fff
FF5733
#AABBCC
#GG0000
#12345
#1234567
rgb(255,0,0)

[ open in Regex Tester → ]

FAQ

What is the difference between 3-digit and 6-digit hex colors?: A 3-digit color like #RGB is shorthand where each digit is doubled, so #ABC expands to #AABBCC. Both represent the same 256³ color space with less precision.
How do I match hex colors with alpha channel?: Add a third alternation for 8-digit hex: #?([a-fA-F0-9]{8}|[a-fA-F0-9]{6}|[a-fA-F0-9]{3}). The last two digits represent the alpha channel.
How do I extract all hex colors from a CSS file?: Use the global flag /g and a pattern with word boundaries to find all hex colors in a block of CSS text. The tester shows all matches highlighted in the input.

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