What is the difference between id and class in HTML
Sep 28, 2025 am 06:30 AM
id is used to uniquely identify a single element, class can be used repeatedly for multiple elements; # select id and . select class in CSS, JavaScript uses getElementById or getElementsByClassName; id is suitable for unique components or anchor links, class is suitable for multiplexing styles or batch operations.
In HTML, both id and class are attributes used to assign identifiers to elements, but they serve different purposes and follow different rules.
Uniqueness: One vs. Many
An id must be unique within a page—only one element should have a particular ID. This makes it ideal for targeting a single, specific element.
A class , on the other hand, can be applied to multiple elements. It's useful when you want to apply the same style or behavior to several elements at once.
Usage in CSS and JavaScript
When styling with CSS:
- Use a # before an id (eg, #header { color: blue; } )
- Use a . before a class (eg, .highlight { background: yellow; } )
In JavaScript, you can select elements by id using document.getElementById("demo") and by class using document.getElementsByClassName("demo") or document.querySelectorAll(".demo") .
Practical Use Cases
Use an id when:
- You're targeting a single, unique element (like a navigation bar or modal)
- You need to create a bookmark link (eg, )
Use a class when:
- Multiple elements share the same style (like buttons or cards)
- You're applying JavaScript behaviors to a group of elements
Basically, think of id as a person's name—unique to one individual—and class as a job title, which many people can share.
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