If you’re a web developer or front-end developer, CSS interview questions are one of the most commonly asked questions.
CSS (Cascading Style Sheets) is used to design and style HTML elements. These days, almost every company checks for CSS knowledge in web design and UI development.
In this article, we will cover Top 50 CSS interview questions with answers which will be helpful for everyone from freshers to experienced candidates.
🔹Basic CSS Interview Questions (For Freshers)
1. What is CSS and why is it used?
Answer: CSS stands for Cascading Style Sheets. It is used to give HTML elements style and layout such as fonts, colors, spacing, and positioning.
2. How many types of CSS are there?
Answer:
- Inline CSS
- Internal CSS
- External CSS
3. What are CSS selectors?
Answer: Selectors are used to target HTML elements. For example,
- Class Selector (.classname)
- ID Selector (#idname)
- Element Selector (p, h1, div)
4. What is the use of z-index property?
Answer: z-index is used to control the stacking order of overlapping elements.
5. What is the difference between Relative, Absolute and Fixed positioning?
Answer:
- Relative: The element will move based on its current position.
- Absolute: The position will be set based on the parent element (nearest positioned ancestor).
- Fixed: It will remain fixed relative to the browser window.
6. Explain the CSS Box Model.
Answer: It includes Content, Padding, Border, and Margin.
7. What are the types of CSS units?
Answer: Absolute (px, cm, mm) and Relative (%, em, rem, vh, vw).
8. Difference between ID and Class in CSS?
Answer: ID is unique and used for one element, Class for multiple elements.
9. Explain the difference between Inline CSS and External CSS.
Answer: Inline applies to only one element, while External can apply to the entire website.
10. How are comments written in CSS?
Answer:
/* This is a CSS comment */
🔹Advanced CSS Interview Questions (For Experienced)
11. Difference between Flexbox and Grid in CSS?
Answer:
- Flexbox: One-dimensional layout system (row or column).
- Grid: Two-dimensional layout system (both row and column).
12. What are CSS variables and how are they declared?
Answer:
:root {
--main-color: blue;
}
div {
color: var(--main-color);
}
13. Where are Media Queries used?
Answer: Media queries are used for responsive web design so that the layout can be adjusted on different screen sizes (mobile, tablet, desktop).
14. Difference between Pseudo-classes and Pseudo-elements?
Answer:
- Pseudo-class: Defines the state of an element. (e.g., :hover, :focus)
- Pseudo-element: Styles a specific part of an element. (e.g., ::before, ::after)
15. Difference between inline-block and block elements?
Answer:
- Block: Takes up the full width (div, p).
- Inline-block: Takes up the width of the content but behaves like a block.
16. Difference between relative, absolute, and fixed positioning?
Answer: Relative – according to your current position, Absolute – according to your parent, Fixed – according to your view port.
17. Difference between relative units em and rem?
Answer: em depends on the parent font-size, rem depends on the root (html) font-size.
18. What is CSS specificity?
Answer: Defines the priority of the selector. Inline > ID > Class > Element.
19. Difference between min-width and max-width?
Answer: min-width = sets minimum width, max-width = maximum width.
20. What are CSS transitions?
Answer: To create smooth animation from one state to another.
21. Why are keyframes used in CSS animations?
Answer: Keyframes define animation at different stages.
22. What is the use of the float property in CSS?
Answer: To align an element to the left or right.
23. Difference between relative length units (%, em, rem) and absolute units (px)?
Answer: Relative are responsive, absolute are fixed.
24. What is CSS Flexbox?
Answer: One-dimensional layout system that aligns items in rows or columns.
25. What is CSS Grid?
Answer: Two-dimensional layout system is (row + column).
26. Difference between Flexbox and Grid?
Answer: Flexbox = single direction, Grid = multi-direction.
27. Where are media queries used?
Answer: To create responsive web design.
28. What are CSS variables?
Answer: To store reusable values.
:root { --main-color: red; }
div { color: var(--main-color); }
29. Difference between relative, sticky, and fixed position?
Answer: Sticky moves with the scroll and gets fixed at some position.
30. What is CSS inheritance?
Answer: Some properties (color, font-size) are inherited from parent to child.
31. Difference between absolute path and relative path in CSS?
Answer: Absolute gives the complete URL, Relative gives the URL of the current file.
32. Difference between CSS2 and CSS3?
Answer: CSS3 includes transitions, animations, flexbox, grid, and media queries.
CSS Performance & Optimization Interview Questions
33. What are CSS sprites?
Answer: Combining multiple images into a single image file to reduce HTTP requests.
34. What is Critical CSS?
Answer: The CSS required for above-the-fold content that loads first.
35. Difference between synchronous and asynchronous CSS loading?
Answer: Synchronous CSS prevents page load, asynchronous parallel load occurs.
36. Difference between reset.css and normalize.css?
Answer: reset.css removes all default styles, normalize.css only standardizes them.
37. How do I know if a CSS file contains unused CSS?
Answer: Tools like Chrome DevTools Coverage or PurgeCSS.
38. Difference between inline critical CSS and deferred CSS?
Answer: Inline is loaded first, deferred is loaded later.
39. How do you optimize large CSS files?
Answer: Minification, Gzip compression, and removing unused CSS.
40. Difference between server-side rendering (SSR) CSS and client-side CSS?
Answer: SSR is rendered on the server first, and client-side CSS is applied later.
41. Are CSS frameworks (Bootstrap, Tailwind) asked in interviews?
Answer: Yes, questions often arise related to comparison and responsive design.
42. Future of CSS – Which features are trending?
Answer: Container queries, Subgrid, Nesting, Cascade layers.
43. How is priority determined in CSS?
Answer: inline > id > class > element > universal.
44. Difference between inline styles and CSS classes?
Answer: Inline for one element, classes for multiple elements.
45. Difference between CSS transition and animation?
Answer: Transition is triggered on state change, animation can run continuously.
46. Difference between inline SVG and background-image SVG?
Answer: Inline SVG is controllable and styleable, background image is not.
47. Difference between relative positioning and sticky positioning?
Answer: Sticky scrolling behaves like relative positioning up to a certain limit and then becomes fixed.
48. What is the overflow property in CSS?
Answer: Overflow handles content – visible, hidden, scroll, auto.
49. Difference between absolute URL and relative URL for background images?
Answer: Absolute gives the complete path, relative depends on the current location.
50. How to add CSS custom fonts?
Answer:
@font-face {
font-family: "MyFont";
src: url("myfont.woff2") format("woff2");
}Conclusion
CSS interview preparation can be easier if you read up on common CSS interview questions beforehand. The 50 frequently asked CSS interview questions in this article will help you ace any web developer or frontend developer interview.
If you’re a fresher, thoroughly study the basics (selectors, properties, units, colors, positioning). If you’re experienced, prepare for advanced concepts (flexbox, grid, animations, responsive design, performance optimization).