Frontend Engineer Interview Guide

Frontend Interview Questions

Screen frontend engineers on browser fundamentals, performance, accessibility, framework judgment, and product craft.

Useful frontend interviews go past framework trivia. Strong candidates reason about rendering, performance, accessibility, and the user experience implications of their choices.

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Section 1

Rendering

Test browser fundamentals: reflow, paint, layout thrashing, and the critical render path.

1. A page jank happens when scrolling. How would you investigate and fix it?

Interview prompt

Strong signal

Uses devtools, profiles main thread, identifies layout/paint cost, and considers will-change or virtualization.

Follow-up probes

  • •How does this differ on mobile?
  • •What if it's only on Safari?

Red flags

  • •Adds will-change everywhere.
  • •No profiling step.
Section 2

Performance

Evaluate bundle size, hydration, and user-perceived speed.

1. Your team's homepage TTI regressed by 1.2s after a recent feature shipped. How do you diagnose it?

Interview prompt

Strong signal

Inspects bundles, network waterfall, hydration cost, and third-party scripts.

Follow-up probes

  • •What budgets would you set?
  • •How do you keep regressions out?

Red flags

  • •Blames a framework without measurement.
  • •No CI budget plan.
Section 3

Accessibility

Check semantic HTML, keyboard interaction, and inclusive defaults.

1. Walk me through how you'd build an accessible modal dialog.

Interview prompt

Strong signal

Discusses focus trapping, return focus, escape, ARIA roles, and screen reader announcements.

Follow-up probes

  • •How do you test it?
  • •What changes for mobile?

Red flags

  • •Only mentions aria-label.
  • •Misses focus management.

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