How to create better themes with CSS variables

CSS variables, also known as custom properties, are a powerful CSS feature that allows developers to define reusable values that can be dynamically adjusted, enhancing the capability to create adaptable and consistent themes across web applications. This guide, updated as of March 2023, delves into the advantages of CSS variables, emphasizing their role in preventing repetitive code, facilitating smooth theme transitions, and maintaining cleaner and more maintainable stylesheets. With broad browser support, including 96.19% of global usage, CSS variables enable developers to efficiently manage theme changes, such as light and dark modes, by setting default values and scoping variables within selectors to ensure inheritance and avoid global scope leakage. The article also explores best practices for utilizing CSS variables, like placing them in the :root for small projects or separate files for larger projects, using descriptive names, and providing fallback values to ensure compatibility with older browsers. Additionally, it offers examples and a step-by-step tutorial on implementing a CSS theme switcher, highlighting the dynamic and versatile application of CSS variables in modern web development.