CssComparisonBeginner · 4 min read

Class vs ID in CSS: Key Differences and When to Use Each

In CSS, a class selector targets one or more elements and can be reused multiple times, while an id selector targets a single unique element on the page. Use class for styling groups of elements and id for unique elements that need specific styles or JavaScript hooks.

⚖️

Quick Comparison

Here is a quick side-by-side comparison of class and id selectors in CSS.

Feature	Class	ID
Selector syntax	`.classname`	`#idname`
Uniqueness	Can be used on multiple elements	Must be unique per page
Specificity	Lower specificity	Higher specificity
Use case	Styling groups of elements	Styling a single unique element
JavaScript targeting	Can select multiple elements	Selects one unique element
Reusability	Reusable across elements	Single use only

⚖️

Key Differences

The main difference between class and id selectors lies in their uniqueness and specificity. An id must be unique within the HTML document, meaning only one element can have that id. This makes it ideal for styling or scripting a single, unique element, like a header or footer.

On the other hand, a class can be assigned to many elements. This allows you to apply the same style to multiple elements easily, such as buttons or cards. Because of this, class selectors have lower specificity than id selectors, so if both target the same element, the id style will override the class style.

In JavaScript, id selectors are often used to quickly find a single element, while class selectors can be used to select groups of elements for batch operations.

⚖️

Code Comparison

Here is an example of using a class selector to style multiple elements with the same style.

html

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Class Example</title>
<style>
  .highlight {
    color: white;
    background-color: teal;
    padding: 5px;
    border-radius: 3px;
  }
</style>
</head>
<body>
  <p class="highlight">This paragraph is highlighted.</p>
  <p class="highlight">This paragraph is also highlighted.</p>
  <p>This paragraph is normal.</p>
</body>
</html>

Output

Two paragraphs with white text on teal background and one normal paragraph.

↔️

ID Equivalent

Here is the same styling applied using an id selector, which can only be used on one element.

html

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>ID Example</title>
<style>
  #uniqueHighlight {
    color: white;
    background-color: teal;
    padding: 5px;
    border-radius: 3px;
  }
</style>
</head>
<body>
  <p id="uniqueHighlight">This paragraph is uniquely highlighted.</p>
  <p>This paragraph is normal.</p>
  <p>This paragraph is normal too.</p>
</body>
</html>

Output

One paragraph with white text on teal background and two normal paragraphs.

🎯

When to Use Which

Choose class when you want to style multiple elements the same way or apply reusable styles across your page. It is flexible and encourages consistent design.

Choose id when you need to style or target a single unique element, such as a main header, footer, or a specific widget. Because id has higher specificity, it can override other styles when necessary.

In general, prefer class for styling and reserve id for unique elements or JavaScript hooks.

✅

Key Takeaways

Use class selectors for styling multiple elements with the same style.

Use id selectors for unique elements that appear only once per page.

id selectors have higher specificity and override class styles if both apply.

class selectors are reusable and flexible for consistent design.

Reserve id mainly for unique styling or JavaScript targeting.