HTML Id

A unique identifier for one element.

✍️ 3 exercises + code challenge in this lesson

❮ Previous Next ❯

The id attribute gives an element a unique name. No two elements on a page may share the same id.

In CSS, select an id with a hash: #header { ... }.
JavaScript finds it with document.getElementById("header").
Links can jump to it with href="#header".

Class vs id

A class can be used on many elements; an id belongs to exactly one element.

Key Takeaways: HTML Id

Mastering HTML Id helps you write clean and reliable HTML code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

HTML Id Code Example

HTML

<style>
  #banner { background: linear-gradient(135deg, #2563EB, #0EA5E9); color: white; padding: 16px; border-radius: 10px; }
</style>

<h1 id="banner">I am unique</h1>
<button onclick="document.getElementById('banner').innerHTML = 'Changed by id!'">Change the banner</button>

Free sign-in required · Google login available

HTML Id Practice Exercises

Check what you learned in “HTML Id”.

/ 3 solved

Fill in the blank

Give the heading a unique id.

<h1 ="main-title">Welcome</h1>

✓ Correct! Not quite. Try again.

Multiple choice

How many elements on a page may share the same id?

Only one Two Any number Ten

✓ Correct! Not quite. Try again.

Code challenge

Give the paragraph the id "intro".

Write the code in the live editor. Your answer is checked automatically.

Free sign-in required · Google login available

to save your exercise progress.

Finished this lesson?

Mark it complete to track your progress.

Stuck on something?

Ask the community in the CodesInTech forum.

Need a developer?

Learning on your own is great — and when you need professional help, our team builds custom software, websites and mobile apps for clients worldwide.

Explore Our Services

HTML Id

Class vs id

💡 Key Takeaways: HTML Id

HTML Id Code Example

HTML Id Practice Exercises

Key Takeaways: HTML Id