When Do You Us Class Vs Id Css

CSS Programming

When I first started learning CSS, one of the things that confused me was when to use a class and when to use an id. It took me a while to fully grasp the differences and when to apply each one effectively. In this article, I’ll share my insights and experience on when to use a class versus an id in CSS.

The Difference Between Class and ID in CSS

Let’s start with the basics. In CSS, a class is a selector that can be applied to multiple elements, while an id is a selector that can only be applied to a single element on a page. This fundamental difference is the key to understanding when to use one over the other.

Using Classes for Reusability

Classes are incredibly useful for applying the same styles to multiple elements across a website. For example, if I have several paragraphs that need to have the same font style, I would create a class in my CSS file and apply it to each paragraph. This allows for easy maintenance and consistency throughout the site.

Utilizing IDs for Specificity

On the other hand, IDs are perfect for targeting a specific element that requires unique styling. In my own projects, I often use an id for the main navigation bar at the top of the page. Since there is typically only one main navigation bar, using an id ensures that the styles are only applied to that specific element.

When to Use Each Selector

Understanding the difference between classes and IDs helps me decide when to use each selector. I primarily use classes for styling elements that share common characteristics, such as buttons, form inputs, or paragraphs. This approach makes it easy to maintain consistency and apply global updates when needed.

On the other hand, I reserve IDs for elements that are unique and require specific styling that should not be shared with any other element on the page. This includes major structural components like headers, footers, and primary navigation bars.

The Importance of Specificity

Another factor to consider is the concept of specificity in CSS. When styling rules conflict, the browser determines which styles to apply based on the specificity of the selectors. In general, IDs have a higher specificity compared to classes. This means that styles defined by an ID will override those defined by a class.


In conclusion, understanding when to use a class versus an id in CSS is crucial for creating maintainable and efficient stylesheets. Classes are ideal for reusable styles that can be applied to multiple elements, while IDs are best suited for unique, specific elements. By utilizing these selectors effectively, I can write cleaner and more manageable CSS code for my projects.