Frontend interviews have evolved. With the rise of tools like React 18, TypeScript, and performance-first architectures, the role of frontend developers has expanded well beyond basic UI implementation.
In fact, industry surveys note an evolving role of frontend developers taking on broader responsibilities beyond just the UI layer a trend toward more holistic engineering roles that require system thinking, architectural awareness, and a strong grasp of performance and accessibility.
According to State of Frontend 2024, 40% of frontend devs say they’re simplifying or refactoring applications to improve performance, rather than chasing new features. Likewise, nearly 77% believe application accessibility is only going to become more important, underscoring how modern frontend work blends user focus with engineering discipline.
This guide is built for frontend devs preparing for technical interviews in 2025. We’ll walk through what hiring managers actually test: from HTML/CSS fundamentals to architecture-level decisions, from async JavaScript to testing strategies.
You’ll get practical advice, detailed examples, and insight into how to handle different frontend interview questions. Whether you're ramping up for your next move or brushing up after a few years in a role, this is your no-nonsense prep guide.
Every interview is different. The questions you get and what you’re expected to know can vary depending on the company, the role, and even the person interviewing you. But if you're looking for a general idea of what to focus on based on your current level, this breakdown can help. Think of it as a zoomed-out view of the bigger picture: what hiring teams typically expect from frontend devs at different stages in their careers.
| Seniority level | What to focus on | Why it matters |
|---|---|---|
| Junior | HTML/CSS fundamentals, basic JavaScript (scope, events), DOM manipulation, accessibility | Establishing strong core knowledge and writing clean, functional UI |
| Mid-Level | Async JavaScript, framework fluency (React/Vue), state management, component design | You're expected to build scalable, maintainable frontend features |
| Senior | System design, performance tuning, testing strategy, and architectural patterns | You’ll be making technical decisions and mentoring others |
| Lead/Principal | Cross-team collaboration, design systems, frontend infra, and strategic planning | You drive the direction of projects and influence engineering culture |
Most interview processes follow a similar structure, though the exact steps can vary depending on the company. Here's a quick overview of the typical stages:
Application or recruiter screen – High-level chat about your background, goals, and timeline.
Initial technical screen – A short coding task, pair programming, or technical Q&A.
Take-home or online assessment – A timed challenge or project-style task to assess real-world coding skills.
Technical interview – Live coding, whiteboarding, or system design conversations with engineers.
Culture or values interview – A non-technical round to explore how you collaborate, communicate, and solve problems.
For a deeper dive into the kinds of technical tasks you might face, check out our Technical Assessment Preparation Guide.
Clean, scalable, and accessible UI is table stakes for any frontend role. Interviews often start with the basics, but they go deeper than "what does semantic HTML mean?" You’re expected to know not just what to use, but why.
Here are some concepts and questions you’re likely to face:
Q: What is semantic HTML, and why does it matter?
💡Semantic elements like <article>, <section>, and <nav> help with SEO, accessibility, and maintainability. They give structure to your page and allow screen readers to interpret content more effectively.
Q: How do you ensure accessibility when building a component?
💡Use ARIA roles only when native HTML doesn’t suffice. Ensure keyboard navigation, use semantic tags, and test with screen readers.
Q: When should you use Flexbox vs Grid?
💡Flexbox is great for 1D layouts (rows or columns). Grid shines for 2D layouts. Bonus: Be ready to sketch out a component layout using both.
Q: How do container queries improve responsive design?
💡Unlike media queries, container queries react to the size of a component’s parent, making truly modular design systems possible.
Q: What’s the difference between em, rem, and % for font sizing?💡em scales from parent, rem from root, and % from container. Know when to use each to maintain consistency.
Q: Why might a style not apply when you expect it to?
💡Specificity conflicts, !important misuse, or style order. Explain how the cascade and specificity levels interact.
Q: What’s CLS, and how do you prevent it?
💡Cumulative Layout Shift happens when content moves after render. Fix it by reserving space for images/fonts and avoiding late-injected content.
Q: How do you optimise CSS for performance?
💡Minify, remove unused styles (via tools like PurgeCSS), and avoid complex selectors.
For more hands-on coding tips, see our Coding Challenge Preparation Guide.
JavaScript is still the heartbeat of the modern frontend. But interviewers aren’t just looking for syntax, they want deep understanding.
Q: What’s a closure and why is it useful?
💡A closure is when a function "remembers" the variables from its outer scope even after that scope has returned. Think event listeners or custom hooks.
Q: Explain this in JavaScript.
💡Depends on context: global, object method, arrow function, class. Be prepared to whiteboard this with examples.
Q: What is the event loop and how does async JavaScript work?
💡Break it down into call stack, task queue, microtasks, and the main thread. Tie it to setTimeout, Promises, and async/await.
Q: Difference between var, let, and const?
💡Cover scope, hoisting, and reassignment. Use real examples.
Q: What are arrow functions good (and bad) for?
💡Lexical this is key. Don’t use them as constructors or when dynamic this is required.
Q: How would you debounce or throttle a function?
💡Debouncing limits how often a function fires. Throttling controls the rate. Interviewers love seeing you implement this from scratch.
Q: How do you prevent memory leaks in JS apps?
💡Avoid lingering event listeners, clear intervals/timeouts, and dereference large unused objects.
TypeScript shows up in more and more frontend roles, especially on larger teams. It’s not just about using types, it’s about thinking in types. Here are some common interview questions and how to handle them without diving too deep into syntax.
Q: What’s the difference between any, unknown, and never?💡any turns off type checking completely. unknown is safer, you have to narrow the type before using it. never means a function that never returns (like one that always throws).
Q: When should you use generics?
💡Use generics when your input and output types are connected, like a function that returns whatever type you give it. It makes your code flexible but still type-safe.
Q: How do you type an object with both required and optional fields?
💡Use optional properties for values that may or may not be passed in (like name?). Interviewers want to hear how you'd design types for real-world flexibility.
Q: What are utility types like Partial, Pick, or Record used for?
💡These let you reshape existing types instead of rewriting them. Think: making everything optional, picking only certain fields, or creating a typed map of values.
Q: What’s the difference between interface and type?
💡Both describe object shapes. Use interface when you want to extend things or model class-like structures. Use type when you need unions or want more flexibility.
Don’t worry about obscure syntax. Focus on how you use types to improve safety, avoid bugs, and help your team work faster. Explain your thinking clearly. That’s what interviewers are really looking for.
Most roles today involve working with frameworks, especially React. But understanding how and why they work is just as important as knowing syntax.
Q: What is the Virtual DOM and how does React use it?
💡React uses the Virtual DOM to batch updates and reduce real DOM mutations. Mention diffing and reconciliation.
Q: When does useEffect run, and how do dependencies work?
💡On mount and when dependencies change. Watch for stale closures and over-fetching.
Q: What’s the difference between state and props?
💡Props are inputs. State is local and mutable. Show how they drive re-renders.
Q: How would you manage global state in a React app?
💡Context API for light state, Redux/Zustand/Recoil for complex needs. Know the trade-offs.
Q: How does React 18’s concurrent rendering improve performance?
💡Prioritises updates, avoids blocking the main thread. Mention startTransition and Suspense.
Angular: How does dependency injection work in Angular?
💡Services are injected into components via constructors. Talk about providers and tree-shaking.
Vue: What is the Composition API and why was it introduced?
💡Encourages better logic reuse and co-located logic. Preferred for scaling.
These are the hands-on coding tasks you’ll often get during live interviews or take-homes.
Manipulating the DOM: e.g. build a simple modal, accordion, or tooltip from scratch
Transforming arrays: filter, sort, reduce or group data from an API
State-driven UI: implement a controlled input form with validation
Async UI: fetch from an API and display loading, error, and success states
Debugging exercise: fix a broken component where props aren’t updating or event isn’t firing
For each challenge, break down:
How you’d structure the solution
What trade-offs exist (e.g. performance vs readability)
What you’d do with more time
System design is no longer just a backend conversation. Frontend engineers are expected to make architectural decisions that impact performance, scalability, and user experience. If you're asked to whiteboard or walk through a design, here's what you'll need to cover:
Q: How would you structure a large-scale React application?
💡Start with modularity. Break features into isolated domains (feature-based folder structure). Use atomic components for reusability. Avoid deeply nested folders. Introduce a design system early to enforce UI consistency.
Include:
Component hierarchy
Route-based code splitting
Lazy loading
Error boundaries
State management layer (e.g. Redux/toolkit, Zustand, or Context + reducer)
Follow-up question to prep for:
"What happens as the app grows? How do you avoid tech debt or performance bottlenecks?"
A structured approach to categorizing state
Awareness of stale data and cache invalidation
Proper usage of memoization/hooks to avoid re-renders
You might include:
Socket client logic
A shared state store
A data throttling mechanism
Error handling/reconnect strategy
Bonus: Add linting/style rules to enforce design system use across teams.
Code splitting
Image and font optimization
Caching strategies (e.g. service workers, CDN)
Avoiding unnecessary renders (memoization, virtualization)
Hiring managers love candidates who understand what the browser gives you out of the box. These questions test your fluency with native APIs beyond just fetch().
Q: What’s the difference between localStorage, sessionStorage, and cookies?
💡All three store data in the browser, but with key differences:
localStorage: persists across sessions, sync API
sessionStorage: cleared on tab close
cookies: smaller capacity, sent with every HTTP request (unless flagged HttpOnly)
Don’t store sensitive data in any of them. Use HttpOnly cookies for auth tokens.
Cache-first vs. network-first strategies
Lifecycle: install, activate, fetch
IndexedDB for more complex storage
Preflight OPTIONS requests
Credentialed requests (withCredentials: true)
Access-Control-Allow-Origin caveats
window, location, navigator, history, etc.window.open() or navigator.geolocation and how you’d handle permissions.performance.mark() / performance.measure()
performance.getEntriesByType()
Explore more in our Backend Developer Interview Guide.
If you’re building production-grade frontend apps, testing should be part of your toolkit. Expect questions on how you ensure the code works before hitting production.
Q: How do you approach testing in frontend development?
💡Start with a testing pyramid:
Unit tests (functions, components)
Integration tests (multiple components working together)
End-to-end (E2E) tests simulating real user flows
Mention tools like:
Jest for unit testing
React Testing Library for component logic
Cypress or Playwright for E2E
async/await in tests and wait for UI updates with utilities like waitFor() from RTL or built-in retries in Cypress.Bonus: Understand fake timers, mocking fetch or axios.
Pro tip: Even if you don’t do full TDD, knowing how to write testable code (e.g. pure functions, separation of concerns) is a big win.
Frontend interviews in 2025 demand more than memorizing syntax. They expect you to:
Write clean, accessible, and scalable UI
Understand the JavaScript engine and browser internals
Architect component-based apps at scale
Debug and test like someone who ships code to prod
It’s not about having all the answers, but showing how you think. When in doubt, talk through your trade-offs, your constraints, and how you’d improve something with more time.
Should I focus more on JavaScript fundamentals or framework knowledge?
Focus on JavaScript first. It’s the foundation for every framework.
How do I prepare for frontend take-home projects?
Treat it like real work: plan first, write clean code, and explain your thinking.
What frontend projects should I highlight on my portfolio for interviews?
Show real-world skills: data fetching, UI state, routing, accessibility.
How do I demonstrate my CSS skills effectively in an interview?
Build a component from scratch and explain your layout choices.
Are data structures and algorithms important for frontend interviews?
Basics matter. Know how to solve common array and string problems.
How do I stay current with rapidly evolving frontend technologies for interviews?
Follow a few solid sources, build small things, and don’t chase everything.
What should I focus on when answering frontend system design questions?
Explain your component structure, state strategy, and performance choices.
How do I explain my problem-solving approach during a frontend coding challenge?
Talk through your steps clearly: understand, plan, solve, improve.