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CSS Variables: Learn to Define Custom Properties

Reading time 2 min
Published Oct 1, 2019
Updated Oct 2, 2019

TL;DR — CSS variables are custom entities that you can define and reuse in your document instead of repeating the same values.

What's a variable in CSS?

Just like you can define your own functions in JavaScript or PHP, you can create custom CSS properties, also known as CSS variables. They contain particular values that you would otherwise need to repeat multiple times in a document (e.g., a specific color).

Using variables in CSS not only saves you time but also simplifies updating the page, as you only need to change the value in one place instead of all across the document.

How to create a CSS variable

To define a variable in CSS, you need to write two dashes (--) in front of its actual name and specify a particular value:

--name: value;

In the example below, we create a custom CSS color variable with a specific color defined in a HEX value:

Example
p {
  --main-text-color: #036627;
}

We recommend using semantic names instead of random ones (e.g., --main-text-color is better than --color1). This will make it easier to read and update the code later.

Using variables in CSS code

To reuse the value you specified in the CSS variable, you need to use the var() function with the variable's name as the value:

Example
p {
  color: var(--main-text-color);
}

CSS variables: useful tips

  • When using the var() function, you can also include a specific value as a fallback. Write it after the variable name and separate the two using a comma.
  • Keep in mind that CSS variables are case-sensitive!