This is what developers have long wanted, even Latest Mailing Database though CSS custom properties (also known as CSS variables) have been Latest Mailing Database around for some time. For example, W3C Module Level 1 is from 2015. But like any new technology, it takes time to gain traction. And we believe that 2021 will have the highest adoption rate since its inception. Why is it so cool? Custom properties are actually CSS variables . You might say, "But Sass has variables." Latest Mailing Database But if you compile Sass into CSS, you'll get CSS. And there are no variables. You can no longer change the value of that variable. $primary: redIs just red. Custom property support Custom Latest Mailing Database properties are well supported everywhere except Internet Explorer However, with custom properties --primary red, And, for example, --primaryyou can redefine to blue. There is no need to compile directly in the Latest Mailing Database browser. To learn more about these CSS tricks What is the difference between CSS variables and preprocessor variables? One clever hack to use them is for custom themes. You can define an Latest Mailing Database HSL value via a variable and allow the user to change the hue using the sliders on the front end. Use the Set Color Scheme feature to connect slider values ​​to CSS variables using JS and BAM.