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Frontend Developer Interview Questions
Frontend interviews have moved away from algorithm puzzles toward building something real in the browser. Expect a live component build, questions about rendering and state, and increasingly a round on accessibility and performance budgets. Hiring managers read frontend CVs for evidence you understand what happens after the component renders — bundle size, Core Web Vitals, and how the UI behaves on a slow device.
Build your story bank freeWhat frontend developer interviews are scored on
Live component build
Implementing something like a typeahead, modal, or data table in a sandbox, usually without a component library. Scored on state handling, edge cases (empty, loading, error), and whether you reach for a keyboard-accessible pattern unprompted.
Browser and rendering fundamentals
The event loop, reflow versus repaint, how the browser paints, and why a given interaction drops frames. This is what separates candidates who use a framework from candidates who understand one.
Accessibility
Semantic markup, focus management, ARIA used correctly and sparingly. Increasingly a scored round rather than a bonus, especially at companies with legal exposure.
Performance
Core Web Vitals, bundle splitting, image strategy, and what you would measure first on a slow page.
Technical frontend developer interview questions
Questions of this shape recur across frontend developer loops. Practise them aloud — interviewers score how you reason, not only where you land.
- Build an accessible typeahead with keyboard navigation and a debounced remote search.
- Explain the event loop, and predict the output order of a snippet mixing setTimeout, a promise, and synchronous logs.
- What causes cumulative layout shift, and how would you fix a page scoring poorly on it?
- When does React re-render a component, and how would you diagnose an unnecessary re-render?
- What is the difference between a controlled and uncontrolled input, and when does that choice actually matter?
- How would you cut a 2MB JavaScript bundle in half without removing features?
- How do you manage focus when a modal opens and closes?
Behavioural questions for frontend developer roles
Prepare one STAR story per theme. A single strong story usually answers two or three of these prompts.
- Tell me about a time you pushed back on a design that would have been bad for accessibility or performance.
- Describe a UI bug that only reproduced for some users. How did you track it down?
- Tell me about working with a designer whose spec was ambiguous.
- Describe a refactor of a component that had grown unmaintainable.
- Tell me about a time you shipped something that regressed a key metric.
Numbers that make frontend developer answers credible
A STAR answer without a result is a story. These are the measures that carry weight in this role.
Questions worth asking your interviewer
- Do you have a performance budget, and what happens when a PR exceeds it?
- How do designers and engineers hand off work here?
- What is your browser and device support matrix?
- Is accessibility tested in CI, or reviewed manually, or neither?
Frontend Developer interview FAQs
What does a Frontend Developer interview actually involve in 2026?+
Most loops now centre on a live build rather than algorithms: you implement a component such as a typeahead, star rating, or nested comment thread in a browser sandbox in 45–60 minutes. Around that you get a fundamentals round (event loop, rendering, CSS layout), often an accessibility or performance round, and a behavioural round. Some companies still include one algorithm screen, but it is increasingly rare for senior frontend roles.
How much JavaScript do I need to know beyond React?+
Enough to explain what React is doing for you. Interviewers commonly ask you to predict output order across setTimeout, promises and microtasks, implement debounce from scratch, or explain closures and prototypal inheritance. Candidates who only know framework idioms tend to fail these. Knowing the platform — the DOM, events, the browser's rendering pipeline — is what differentiates mid from senior in this role.
What belongs on a Frontend Developer CV?+
Measurable interface outcomes. Bundle size reduced, Lighthouse or Core Web Vitals scores moved, conversion or task-completion rates improved, accessibility violations closed. "Cut LCP from 4.1s to 1.6s on the product page, lifting mobile conversion 8%" is worth more than any list of frameworks, because it proves you connect frontend work to user behaviour. Include a link to deployed work — frontend is one of the few roles where reviewers actually click.
Do I need a portfolio site as a Frontend Developer?+
A link to something real matters more than a portfolio site as such. Two or three deployed projects with visible source code do the job, and hiring managers will look at your CSS and your accessibility choices. A portfolio site that is itself slow or inaccessible actively hurts you, so if you build one, treat it as a work sample and hold it to the standards you would claim in an interview.
Need the CV before the interview?
See frontend developer CV examples, before/after bullets, and the metrics reviewers look for.
Other interview guides
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