CSS (Cascading Style Sheets) is one of the most important skills for any front-end or web developer. Whether you are a fresher preparing for your first interview or an experienced developer switching roles, CSS interview questions are almost guaranteed in every web-related interview
Many candidates know CSS basics but still struggle during interviews because interviewers don’t ask only definitions. They focus on real-world usage, browser behavior, layout concepts, responsiveness, performance, and tricky scenarios that developers face in daily work. That’s why preparing from random questions is not enough.
In this blog, we have carefully compiled the most asked CSS interview questions based on:
- Real interview experiences
- Common patterns asked by companies
- Frequently repeated CSS concepts
- Tricky and confusing topics interviewers love
This guide covers CSS basics to advanced concepts, explained in simple and clear language, so you can understand the “why” behind each answer — not just memorize it. Whether your interview is for frontend developer, UI developer, Angular/React developer, or full-stack role, this CSS interview preparation blog will help you build strong confidence.
CSS Fundamentals
Q. Explain the difference between type (element), class, and ID selectors in CSS.
Type (element) selector targets all HTML elements of a specific type, like p or div, and applies styles to every such element on the page.
Class selector targets elements with a specific class name (using .), can be reused multiple times, and is useful for styling groups of elements.
ID selector targets a single unique element (using #), should be used once per page, and has higher specificity than type and class selectors.
Q. What is an attribute selector in CSS and how would you use it?
An attribute selector in CSS is used to target HTML elements based on their attributes or attribute values. It helps apply styles without relying on classes or IDs and is very useful in form styling. For example, input[type=”text”] { border: 1px solid #000; } styles only text input elements.
Q. What does the universal selector (*) do, and when might you use it?
The universal selector (*) selects all elements on a page and is commonly used for applying global styles like resetting margins, padding, or setting box-sizing.
Q. How do grouping selectors work in CSS and why are they useful?
Grouping selectors allow you to apply the same CSS rules to multiple selectors by separating them with commas. They reduce code repetition and make stylesheets cleaner and easier to maintain.
Example: h1, h2, p { color: #333; } applies the same style to all listed elements.
Q. What is the difference between inline, internal, and external CSS, and when should you use each?
Inline CSS is written directly inside HTML elements and is useful for quick, one-off styling but not recommended for large projects.
Internal CSS is placed inside a <style> tag in the <head> and is suitable for styling a single page.
External CSS is written in a separate .css file and is best for large websites because it improves reusability, maintainability, and performance.
Q. What is the difference between em and rem units in CSS, and when should you use each?
em is relative to the font size of the parent element, which can cause scaling issues when nested.
rem is relative to the root (html) font size and is preferred for consistent, scalable layouts.
Box Model
Q. What are the four components of the CSS Box Model and how do they affect an element’s layout?
The CSS Box Model consists of content, padding, border, and margin. The content is the actual text or image inside the element, padding creates space between the content and the border, and the border wraps around the padding and content to define the element’s boundary. Margin is the outermost space that separates an element from other elements on the page.
Together, these components control the element’s total size, spacing, and how it is positioned within the layout.
Q. How does padding differ from margin in the CSS Box Model?
Padding creates space inside an element between its content and border, affecting the element’s overall size. Margin creates space outside the element, separating it from surrounding elements without changing its internal area.
Q. What is the difference between box-sizing: content-box and box-sizing: border-box in CSS?
box-sizing: content-box is the default behavior where width and height apply only to the content area.
Padding and border are added outside the specified width and height, increasing the total size.
box-sizing: border-box includes padding and border within the defined width and height. This makes layout calculations easier and prevents unexpected size overflow.
Specificity & Cascade
Q. How does CSS specificity work (Inline > ID > Class > Element) and how are style conflicts resolved when multiple rules apply to the same element?
CSS specificity determines which style rule is applied when multiple rules target the same element, following the order Inline styles > ID selectors > Class/attribute selectors > Element selectors. A selector with higher specificity always overrides a lower one, regardless of where it appears in the stylesheet.
When two rules have the same specificity, the rule written later in the CSS takes priority due to the cascade. If conflicts still exist, inline styles and the !important rule can override others, though !important should be avoided for maintainable code.
Q. What is the difference between cascade and inheritance in CSS, and which CSS properties inherit automatically from parent elements?
The cascade in CSS refers to how the browser decides which CSS rule to apply when multiple rules target the same element, based on specificity, importance, and source order. Inheritance, on the other hand, means that some CSS properties are automatically passed down from parent elements to their children unless overridden.
Properties related to text and fonts inherit by default, such as color, font-family, font-size, font-style, font-weight, line-height, visibility, and text-align. Layout and box model properties like margin, padding, border, width, and height do not inherit automatically.
Q. What is !important in CSS, why is it considered a bad practice, and in which rare situations is it acceptable to use it?
!important forces a CSS rule to override all other styles, ignoring specificity and cascade order.
It is considered bad practice because it makes CSS harder to debug and maintain.
It should be used only in rare cases like overriding third-party library styles when no other option exists.
Flexbox
Q. What does display: flex do, and how does it change the layout behavior of child elements compared to block or inline layouts?
display: flex turns a container into a flexbox, allowing its child elements to be arranged in a flexible, responsive row or column layout. Unlike block or inline layouts, flex items can automatically adjust their size, spacing, and alignment within the container, making it easier to create complex layouts like centered content, evenly spaced elements, or dynamic grids without relying on floats or manual positioning.
Q. What is the difference between justify-content, align-items, and align-self in Flexbox?
justify-content aligns flex items horizontally along the main axis, align-items aligns them vertically along the cross axis, and align-self overrides align-items for individual flex items.
Q. How do flex-direction and flex-wrap control the flow and wrapping of flex items?
flex-direction determines the main axis and the order of flex items (row, row-reverse, column, column-reverse), while flex-wrap controls whether items stay on a single line or wrap onto multiple lines when they overflow the container.
Q. What are flex-grow, flex-shrink, and flex-basis, and how do they work together to control item sizing?
flex-grow controls how much a flex item can expand relative to others, flex-shrink determines how it contracts when space is limited, and flex-basis sets the initial size of the item; together, they define how items grow, shrink, and start within a flex container.
Q. How does Flexbox handle space distribution when container size changes, and which properties influence this behavior the most?
Flexbox distributes space dynamically based on the container size, adjusting flex items according to flex-grow, flex-shrink, and flex-basis.
Properties like justify-content control spacing along the main axis, while align-items and align-content manage spacing along the cross axis, ensuring items remain properly aligned and proportioned as the container resizes.
Position Property
Q. What are the different values of the CSS position property and how do they differ?
static: Default positioning; elements follow the normal document flow and ignore top, bottom, left, or right properties.
relative: Element is positioned relative to its normal position; you can adjust its position using top, bottom, left, or right without affecting other elements.
absolute: Element is removed from the normal flow and positioned relative to the nearest positioned ancestor (not static).
fixed: Element is removed from the flow and stays fixed relative to the viewport, even when the page is scrolled.
sticky: Element toggles between relative and fixed positioning depending on the scroll position; it behaves like relative until a defined scroll threshold is reached.
The CSS position values differ in how they place elements and affect document flow. static follows the normal flow with no offset control, while relative moves an element relative to its original position without affecting others. absolute removes the element from the flow and positions it relative to the nearest positioned ancestor, whereas fixed locks it to the viewport regardless of scrolling. sticky combines relative and fixed behavior, staying in flow until a scroll threshold is reached, then acting like fixed.
Q. What is the difference between relative and absolute positioning?
Relative positioning moves an element relative to its normal position without affecting other elements.
Absolute positioning removes the element from the normal flow and positions it relative to the nearest positioned ancestor.
Q. How does position: fixed behave compared to position: sticky?
position: fixed keeps an element locked relative to the viewport, so it stays visible even when the page is scrolled. In contrast, position: sticky behaves like relative within the normal flow until a specified scroll point is reached, after which it “sticks” in place like a fixed element.
Q. How does the top, right, bottom, and left properties work with positioned elements?
The top, right, bottom, and left properties define remember that element’s offset from its reference point when a position other than static is applied. For relative elements, they shift the element from its normal position, while for absolute and fixed elements, they position the element relative to the nearest positioned ancestor or the viewport.
Q. In which scenarios would you use position: sticky in real projects?
position: sticky is commonly used for elements that need to remain visible only within a certain scroll area, such as sticky headers, section titles, navigation bars, filters or category menus, and table headers. It is ideal when you want an element to scroll normally at first and then stick to a position once the user reaches a specific point, improving usability without removing the element from the document flow.
Media Queries
Q. What are media queries in CSS and why are they used?
Media queries in CSS allow you to apply styles based on device characteristics like screen size, resolution, or orientation.
They are used to create responsive designs that adapt layouts for different devices.
Q. What is the difference between mobile-first and desktop-first media query approaches?
The mobile-first approach starts by writing CSS for smaller screens and progressively adds styles for larger screens using min-width media queries.
It ensures a responsive design optimized for mobile devices first.
The desktop-first approach starts with styles for larger screens and adjusts them for smaller devices using max-width media queries.
Mobile-first is generally preferred today due to better performance and accessibility on mobile devices.
Q. How do min-width and max-width media queries work?
min-width media queries apply styles when the viewport width is greater than or equal to the specified value. They are commonly used in mobile-first designs to progressively enhance layouts for larger screens.
max-width media queries apply styles when the viewport width is less than or equal to the specified value. They are often used in desktop-first approaches to adjust layouts for smaller screens.
Together, these queries allow developers to create responsive and adaptive designs across different devices.
Q. Can you target specific devices or screen resolutions using media queries?
Yes, media queries can target specific devices or screen resolutions by using features like width, height, resolution, and orientation.
Grid vs Flexbox
Q. What is the main difference between CSS Grid and Flexbox?
CSS Grid is designed for two-dimensional layouts, handling both rows and columns simultaneously.
Flexbox is one-dimensional, managing either a row or a column at a time for flexible item alignment.
Q. When should you use Grid instead of Flexbox?
Use CSS Grid when you need a two-dimensional layout with both rows and columns, such as complex web pages or dashboards.
It is ideal for creating precise grid structures, overlapping elements, or consistent spacing across both axes.
Flexbox is better suited for simpler, one-dimensional layouts like navbars, menus, or aligning items in a single row or column.
Q. Can Grid and Flexbox be used together in the same layout?
Yes, Grid and Flexbox can be combined in the same layout to leverage their strengths.
For example, Grid can define the overall page structure while Flexbox handles alignment and spacing within individual grid items.
Q. How does alignment differ in Grid compared to Flexbox?
In CSS Grid, alignment can be controlled along both rows and columns using properties like align-items, justify-items, align-content, and justify-content.
Flexbox primarily aligns items along one axis at a time—main axis with justify-content and cross axis with align-items.
Grid provides more precise two-dimensional control, while Flexbox is simpler for one-dimensional layouts.
CSS is more than just styling. It defines user experience, responsiveness, accessibility, and performance of a website. Interviewers know this very well, which is why CSS questions are often concept-based, practical, and scenario-driven.
By preparing the questions shared in this blog, you will not only be ready to answer confidently in interviews, but you’ll also improve your day-to-day frontend development skills. Understanding how CSS works internally, like box model, specificity, layout systems, positioning, and responsiveness, gives you a strong edge over others.
We will update this blog regularly with:
- New and trending CSS interview questions
- Advanced and tricky questions asked by companies
- Modern CSS features and best practices
- Real interview-based scenarios
So make sure to bookmark this page and visit again whenever you are preparing for an interview or revising CSS concepts.
If you found this blog helpful, feel free to share it with your friends or colleagues who are preparing for frontend interviews.
Happy learning and all the best for your CSS interviews.
