CSS Variables, also known as Custom Properties, are entities that allow you to store specific values to be reused throughout your stylesheet. They provide a way to create more maintainable and flexible CSS code.

Defining CSS Variables

To define a CSS variable, use double dashes (--) followed by the variable name. Variables are typically declared within a selector, often the :root pseudo-class for global scope:

:root {
  --primary-color: #3498db;
  --font-size: 16px;
}

Using CSS Variables

To use a CSS variable, employ the var() function:

body {
  background-color: var(--primary-color);
  font-size: var(--font-size);
}

Benefits of CSS Variables

Improved code maintainability
Easy theme switching
Reduced repetition in stylesheets
Dynamic value changes with JavaScript

Fallback Values

You can provide fallback values in case a variable is not defined:

p {
  color: var(--text-color, #333);
}

Scope and Inheritance

CSS Variables follow the cascading nature of CSS. They can be redefined within different selectors, creating a scoped value:

.button {
  --button-color: blue;
  background-color: var(--button-color);
}

.button.danger {
  --button-color: red;
}

JavaScript Integration

CSS Variables can be manipulated using JavaScript, allowing for dynamic style changes:

document.documentElement.style.setProperty('--primary-color', '#ff0000');

Browser Support

CSS Variables are supported in all modern browsers. For older browsers, consider using a polyfill or providing fallback values.

Best Practices

Use meaningful and descriptive variable names
Organize variables logically, grouping related properties
Consider using a naming convention, such as BEM, for larger projects
Provide fallback values for critical styles

Related Concepts

To further enhance your CSS skills, explore these related topics:

By mastering CSS Variables, you'll be able to create more flexible and maintainable stylesheets, improving your overall web development workflow.