CSS Interview Questions: Beginner to Advanced

In this article, you’ll find 30 real-life CSS interview questions for frontend developers. These questions are asked in interviews from fresher to experienced level. Each question is deeply connected to the next, forming a logical learning path. Answers are written in easy and professional English so you can remember and explain confidently during interviews.

🔰 Beginner Level CSS Interview Questions (1–10)

1. What is CSS and why do we use it?

Answer: CSS stands for Cascading Style Sheets. We use it to style HTML elements — such as colors, fonts, spacing, layout, etc. Without CSS, web pages would look plain and boring.

2. What are the different types of CSS?

Answer:

Inline CSS – written inside an HTML tag using the style attribute.
Internal CSS – written inside <style> tags in the <head> section.
External CSS – written in a separate .css file and linked using <link> tag.

3. What is the difference between class and ID in CSS?

Answer:

.class can be used on multiple elements.
#id is unique and used for one element only.
Example:

.red { color: red; }   /* class */
#header { font-size: 24px; }  /* id */

4. What is the Box Model in CSS?

Answer:
The CSS box model represents how every HTML element is structured:

Content → Padding → Border → Margin
Each part affects the element’s space and layout.

5. What is the difference between `padding` and `margin`?

Answer:

padding: space inside the element, between content and border.
margin: space outside the element, between border and other elements.

6. What are pseudo-classes in CSS?

Answer:
Pseudo-classes define a special state of an element.
Example: :hover, :focus, :first-child

button:hover {
  background-color: blue;
}

7. How do you make a website responsive using CSS?

Answer:
You can use:

Media Queries (@media)
Flexible layouts (like percentages or vw, vh)
Flexbox and Grid
Example:

@media (max-width: 768px) {
  .container {
    flex-direction: column;
  }
}

8. What are the units used in CSS?

Answer:

Absolute: px, cm, mm, in
Relative: em, rem, %, vw, vh

9. What is the difference between `em` and `rem`?

Answer:

em: relative to the parent element’s font size.
rem: relative to the root (html) font size.

10. What is specificity in CSS?

Answer:
Specificity is a set of rules that determine which CSS rule is applied when multiple rules target the same element.
Order of power:

Inline style (style="...")
ID selectors (#id)
Class selectors (.class)
Element selectors (div, p)

🚀 Intermediate to Advanced CSS Interview Questions (11–30)

11. What is Flexbox in CSS?

Answer:
Flexbox (Flexible Box) is a layout module in CSS that allows you to arrange items in rows or columns easily, even when their size is dynamic.

12. What are the main properties of a Flex container?

Answer:
Set on the container using display: flex;

flex-direction
justify-content
align-items
flex-wrap
align-content

13. What does `justify-content` do in Flexbox?

Answer:
It controls the horizontal alignment of flex items.
Values:

flex-start, flex-end, center, space-between, space-around, space-evenly

14. What is `align-items` used for in Flexbox?

Answer:
It aligns items vertically in the container.
Values:

stretch (default), flex-start, flex-end, center, baseline

15. How is `align-self` different from `align-items`?

Answer:

align-items applies to all items in the container.
align-self overrides alignment for a specific item only.

16. What is the use of `flex-grow`, `flex-shrink`, and `flex-basis`?

Answer:
These control how flex items grow, shrink, and take up space:

flex-grow: how much it can grow
flex-shrink: how much it can shrink
flex-basis: default size before space is distributed

17. What is the shorthand for these properties?

Answer:
You can write them as:

flex: 1 0 200px; /* grow shrink basis */

18. What is CSS Grid and how is it different from Flexbox?

Answer:

Flexbox: One-dimensional layout (row or column)
Grid: Two-dimensional layout (rows and columns)

Use Grid for complex layouts and Flexbox for smaller components.

19. How do you define a CSS Grid container?

Answer:

display: grid;
grid-template-columns: 1fr 1fr 1fr;
grid-template-rows: auto auto;

20. What are Grid lines, Grid tracks, and Grid areas?

Answer:

Grid lines: vertical and horizontal lines that divide the grid.
Grid tracks: space between two lines (rows or columns).
Grid area: rectangular space formed by joining tracks.

21. What are media queries and why are they used?

Answer:
Media queries allow you to apply different styles based on device width, height, resolution, etc.
They make websites responsive.

22. What is the difference between `absolute`, `relative`, and `fixed` positioning in CSS?

Answer:

relative: moves from original position.
absolute: positions from the nearest positioned ancestor.
fixed: always fixed to the viewport.

23. What is `z-index` and how does it work?

Answer:
z-index controls the stacking order of elements. Higher z-index means it will appear on top.

24. What is the difference between `visibility: hidden` and `display: none`?

Answer:

visibility: hidden hides the element but still takes up space.
display: none removes the element from the layout.

25. What are transitions in CSS?

Answer:
Transitions allow you to smoothly change properties over time.
Example:

button {
  transition: background-color 0.3s ease;
}

26. What are CSS animations?

Answer:
Animations let you define keyframes for styling changes over time.

@keyframes move {
  from { left: 0; }
  to { left: 100px; }
}

27. What is the difference between `min-width`, `max-width`, and `width`?

Answer:

width: fixed value.
min-width: minimum allowed width.
max-width: maximum allowed width.

They help in responsive design.

28. What is the difference between `auto`, `initial`, and `inherit` in CSS?

Answer:

auto: browser decides the value.
initial: resets to default value.
inherit: inherits value from the parent.

29. How to improve CSS performance?

Answer:

Use shorthand properties
Minimize CSS file size
Avoid unnecessary selectors
Use class names instead of element selectors
Combine files and use caching

30. Which is better for layouts: Flexbox or Grid?

Answer:
It depends on the design:

Use Flexbox for 1D layouts (navbar, buttons row)
Use Grid for 2D layouts (entire page layout)

Both can be used together in real-world projects.

✅ Conclusion

These 30 CSS interview questions are picked from real interview experiences. They are interlinked, progressing from beginner to expert level, and they will help you explain clearly during actual interviews. Practice the answers, try them in real code, and keep experimenting with CSS properties.

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✅ Part 3: Top 30 CSS Interview Questions and Answers (Beginner to Advanced) – Real Interview Style

Table of contents

🔰 Beginner Level CSS Interview Questions (1–10)

1. What is CSS and why do we use it?

2. What are the different types of CSS?

3. What is the difference between class and ID in CSS?

4. What is the Box Model in CSS?

5. What is the difference between `padding` and `margin`?

6. What are pseudo-classes in CSS?

7. How do you make a website responsive using CSS?

8. What are the units used in CSS?

9. What is the difference between `em` and `rem`?

10. What is specificity in CSS?

🚀 Intermediate to Advanced CSS Interview Questions (11–30)

11. What is Flexbox in CSS?

12. What are the main properties of a Flex container?

13. What does `justify-content` do in Flexbox?

14. What is `align-items` used for in Flexbox?

15. How is `align-self` different from `align-items`?

16. What is the use of `flex-grow`, `flex-shrink`, and `flex-basis`?

17. What is the shorthand for these properties?

18. What is CSS Grid and how is it different from Flexbox?

19. How do you define a CSS Grid container?

20. What are Grid lines, Grid tracks, and Grid areas?

21. What are media queries and why are they used?

22. What is the difference between `absolute`, `relative`, and `fixed` positioning in CSS?

23. What is `z-index` and how does it work?

24. What is the difference between `visibility: hidden` and `display: none`?

25. What are transitions in CSS?

26. What are CSS animations?

27. What is the difference between `min-width`, `max-width`, and `width`?

28. What is the difference between `auto`, `initial`, and `inherit` in CSS?

29. How to improve CSS performance?

30. Which is better for layouts: Flexbox or Grid?

✅ Conclusion

🔔 Stay Connected

Subscribe to my newsletter

Payal Porwal

Payal Porwal

✅ Part 3: Top 30 CSS Interview Questions and Answers (Beginner to Advanced) – Real Interview Style

Table of contents

🔰 Beginner Level CSS Interview Questions (1–10)

1. What is CSS and why do we use it?

2. What are the different types of CSS?

3. What is the difference between class and ID in CSS?

4. What is the Box Model in CSS?

5. What is the difference between padding and margin?

6. What are pseudo-classes in CSS?

7. How do you make a website responsive using CSS?

8. What are the units used in CSS?

9. What is the difference between em and rem?

10. What is specificity in CSS?

🚀 Intermediate to Advanced CSS Interview Questions (11–30)

11. What is Flexbox in CSS?

12. What are the main properties of a Flex container?

13. What does justify-content do in Flexbox?

14. What is align-items used for in Flexbox?

15. How is align-self different from align-items?

16. What is the use of flex-grow, flex-shrink, and flex-basis?

17. What is the shorthand for these properties?

18. What is CSS Grid and how is it different from Flexbox?

19. How do you define a CSS Grid container?

20. What are Grid lines, Grid tracks, and Grid areas?

21. What are media queries and why are they used?

22. What is the difference between absolute, relative, and fixed positioning in CSS?

23. What is z-index and how does it work?

24. What is the difference between visibility: hidden and display: none?

25. What are transitions in CSS?

26. What are CSS animations?

27. What is the difference between min-width, max-width, and width?

28. What is the difference between auto, initial, and inherit in CSS?

29. How to improve CSS performance?

30. Which is better for layouts: Flexbox or Grid?

✅ Conclusion

🔔 Stay Connected

Subscribe to my newsletter

Payal Porwal

Payal Porwal

5. What is the difference between `padding` and `margin`?

9. What is the difference between `em` and `rem`?

13. What does `justify-content` do in Flexbox?

14. What is `align-items` used for in Flexbox?

15. How is `align-self` different from `align-items`?

16. What is the use of `flex-grow`, `flex-shrink`, and `flex-basis`?

22. What is the difference between `absolute`, `relative`, and `fixed` positioning in CSS?

23. What is `z-index` and how does it work?

24. What is the difference between `visibility: hidden` and `display: none`?

27. What is the difference between `min-width`, `max-width`, and `width`?

28. What is the difference between `auto`, `initial`, and `inherit` in CSS?