When styling HTML elements with CSS, two of the most commonly used selectors are ID and Class. While both serve to target and style elements, they function differently and have distinct use cases.
In this blog, we’ll explain the difference between ID and Class in CSS, how to use them with examples, and when you should choose one over the other.
🔹 What is an ID Selector in CSS?
An ID selector is used to style a single, unique HTML element. It is defined using a # (hash) symbol followed by the ID name.
✅ Syntax:
#myElement {
color: red;
font-size: 20px;
}
✅ HTML Usage:
<p id="myElement">This paragraph has an ID.</p>
✅ Key Points:
- Each ID must be unique on the page.
- IDs are often used for specific styling or targeting with JavaScript.
- IDs have higher specificity than classes.
🔸 What is a Class Selector in CSS?
A Class selector is used to style multiple elements with the same class. It is defined using a . (dot) followed by the class name.
✅ Syntax:
.highlight {
background-color: yellow;
font-weight: bold;
}
✅ HTML Usage:
<p class="highlight">This paragraph is highlighted.</p>
<div class="highlight">This div is also highlighted.</div>
✅ Key Points:
- A class can be used on multiple elements.
- One element can have multiple classes.
- Ideal for reusable styling patterns.
🆚 ID vs Class – Key Differences
| Feature | ID Selector (#id) | Class Selector (.class) |
|---|---|---|
| Uniqueness | Must be unique per element | Can be reused on many elements |
| Syntax | #idName | .className |
| Specificity | Higher | Lower |
| Reusability | Not reusable | Highly reusable |
| Use Case | Single, specific elements | Group of similar elements |
📝 When to Use ID or Class?
- ✅ Use an ID when:
- You are targeting a unique element (e.g., site header, main section).
- You want high specificity.
- You need to interact with the element via JavaScript.
- ✅ Use a Class when:
- You want to apply the same style to multiple elements.
- You are building reusable CSS rules.
- You need flexibility and scalability in styling.
💡 Pro Tip: Avoid Overusing IDs in CSS
While IDs are useful, they can limit flexibility in your CSS and may lead to specificity conflicts. As a best practice, rely on classes for styling and reserve IDs for JavaScript hooks or anchors.
✅ Conclusion
Both IDs and Classes are fundamental to CSS and serve different purposes. Understanding their differences and appropriate use cases helps you write clean, maintainable, and scalable stylesheets.
✨ Rule of Thumb: Use classes for styling, use IDs for unique identification or scripting.
