Learn CSS Variables in 5 minutes – A Tutorial for Beginners

As a full-stack developer, I‘ve seen firsthand how CSS variables (also known as CSS custom properties) have revolutionized the way we write and maintain stylesheets. In this comprehensive tutorial, I‘ll share my experience and insights to help you quickly grasp the fundamentals of CSS variables and start using them in your own projects with confidence.

What are CSS variables?

CSS variables are entities that allow you to store and reuse specific values throughout your stylesheet. They follow a simple syntax:

:root {
  --main-color: #ff0000;
}

.my-element {
  color: var(--main-color);
}

In this example, –main-color is a CSS variable holding the value #ff0000 (red). The .my-element selector uses the var() function to apply that value to its color property.

Why use CSS variables?

From a developer‘s perspective, CSS variables offer several key benefits:

1. Improved maintainability: By centralizing common values as variables, you can update them in one place and have those changes propagate throughout your stylesheet. This is much more efficient than searching for and replacing hard-coded values.

2. Enhanced readability: Well-named variables make your code more self-documenting and easier for other developers (or your future self) to understand at a glance.

3. Increased flexibility: CSS variables can be changed dynamically with JavaScript, opening up exciting possibilities for user customization and theming.

4. Simplified responsive design: You can define different variable values within media queries, making it easy to adjust styles based on screen size or other conditions.

Here‘s a real-world example from my experience: On a large e-commerce project, we used CSS variables extensively for colors, typography, and spacing. When the client requested a complete redesign, we only needed to update the variable values in one place, and the entire site adapted seamlessly. This saved us countless hours compared to manually updating each individual property.

CSS variables vs. preprocessor variables

You might be wondering how CSS variables compare to variables in preprocessors like Sass or Less. While they serve similar purposes, there are a few key differences:

Feature	CSS Variables	Preprocessor Variables
Browser support	High (95.71% globally)	Requires compilation
Scope	Cascade and inherit like regular CSS properties	Limited to preprocessor scope
DOM access	Yes, can be manipulated with JavaScript	No, compiled away before reaching the browser
Runtime updates	Yes	No

In my opinion, CSS variables are the future of styling because they work natively in the browser and offer more flexibility. However, preprocessor variables can still be useful in certain situations, such as complex calculations or code organization.

Best practices for using CSS variables

To get the most out of CSS variables, follow these tips:

1. Use meaningful names: Choose clear, descriptive names for your variables that convey their purpose. Prefer –main-text-color over –color-1.

2. Organize your variables: Group related variables together and consider prefixing them for easier identification. For example, –color-primary, –color-secondary, –font-size-small, –font-size-large, etc.

3. Leverage cascading and inheritance: Define global variables on the :root pseudo-class and override them in more specific selectors as needed.

4. Provide fallback values: For browsers that don‘t support CSS variables, provide a fallback value before the variable declaration:

   .my-element {
     color: blue;
     color: var(--main-color);
   }

5. Use variables for theming: CSS variables excel at creating multiple themes or color schemes. Define a set of theme-specific variables, then dynamically switch between them with JavaScript:

   :root {
     --light-bg: white;
     --light-text: black;
     --dark-bg: black;
     --dark-text: white;
   }
   
   .light-theme {
     --bg: var(--light-bg);
     --text: var(--light-text);
   }
   
   .dark-theme {
     --bg: var(--dark-bg);  
     --text: var(--dark-text);
   }

   // Toggle theme
   document.body.classList.toggle(‘dark-theme‘);

Real-world examples and use cases

Let‘s look at some practical applications of CSS variables:

1. Responsive typography: Define a base font size variable, then use it to scale other elements proportionally:

   :root {
     --base-font-size: 16px;
   }
   
   @media screen and (max-width: 768px) {
     :root {
       --base-font-size: 14px;
     }
   }
   
   h1 {
     font-size: calc(var(--base-font-size) * 2.5);
   }
   
   p {
     font-size: var(--base-font-size);
   }

2. Consistent spacing: Create variables for common spacing values to maintain consistency and make global adjustments easy:

   :root {
     --spacing-small: 8px;
     --spacing-medium: 16px;
     --spacing-large: 24px;
   }
   
   .card {
     padding: var(--spacing-medium);
     margin-bottom: var(--spacing-large);
   }

3. Themes and customization: Allow users to customize the appearance of your site or app by exposing CSS variables:

   :root {
     --primary-color: #ff0000;
     --bg-color: white;
   }

   // Update variables based on user preferences
   document.documentElement.style.setProperty(‘--primary-color‘, userColor);
   document.documentElement.style.setProperty(‘--bg-color‘, userBgColor);

4. Reusable components: Create modular, reusable components by defining variables for their key properties:

   .button {
     --btn-bg-color: #007bff;
     --btn-text-color: white;
     --btn-padding: 8px 16px;
   
     background-color: var(--btn-bg-color);
     color: var(--btn-text-color);
     padding: var(--btn-padding);
   }
   
   .button-secondary {
     --btn-bg-color: #6c757d;
   }

   This makes it easy to create variations of the component by overriding its variables.

Potential drawbacks and gotchas

While CSS variables are incredibly useful, there are a few potential drawbacks and gotchas to be aware of:

1. Browser support: While global support for CSS variables is high, some older browsers like Internet Explorer don‘t support them. Always provide fallback values for critical properties.

2. Specificity issues: Because CSS variables cascade and inherit, it‘s possible to run into specificity issues if you‘re not careful. Keep an eye on your selector specificity and use the !important declaration sparingly.

3. Performance considerations: Using CSS variables extensively can potentially impact performance, especially when combined with complex calculations or animations. Be mindful of your usage and profile your code if you encounter issues.

4. Learning curve: If you‘re coming from a preprocessor background, there may be a slight learning curve as you adjust to the different syntax and behavior of CSS variables. Take the time to experiment and practice to solidify your understanding.

Conclusion and further reading

CSS variables are a powerful tool that every web developer should have in their toolkit. By allowing you to store and reuse values throughout your stylesheets, they make your code more maintainable, readable, and flexible.

As a full-stack developer who has used CSS variables extensively in production, I can attest to their effectiveness in streamlining development and making global style changes a breeze. Whether you‘re building a small site or a large-scale application, CSS variables can help you write cleaner, more efficient code.

To dive deeper into CSS variables and related topics, check out these resources:

• MDN Docs – Using CSS custom properties
• CSS Tricks – A Complete Guide to CSS Custom Properties
• Smashing Magazine – It‘s Time To Start Using CSS Custom Properties
• web.dev – CSS Variables: Why Should You Care?
• CSS Variables Cheat Sheet

I hope this tutorial has given you a solid foundation in CSS variables and inspired you to start using them in your own projects. Trust me, once you experience the benefits firsthand, you‘ll never want to go back to hard-coded values again!

Happy coding! 🚀