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🌐 Interview Prep

Web & Frontend

HTML, CSS layout, the DOM, HTTP, browsers, React, security and accessibility: front-end and full-stack interview staples.

📘 Learn it from scratch

Visual, hands-on lessons for every pattern in this topic. Do the lesson, then come back and the questions click.

HTML: Structure & SemanticsForms & InputsThe Box ModelCSS Layout with FlexboxResponsive Design for PhonesHTTP: Requests & ResponsesState, Events & Reducers

100 questions, most asked first

Ordered so the most useful questions for learning each pattern come first.

Any difficulty Easy Medium Hard

All patterns HTTP & APIs Storage & caching Box model Flexbox Web security React HTML Accessibility Responsive design CSS Grid & positioning Browser & performance State management Forms DOM & events

#1What happens when you type a URL and press Enter?HTTP & APIsMediumFree #6CSS specificity and the cascadeBox modelMediumFree #8What is CORS?Web securityMediumFree #9Cross-site scripting (XSS)Web securityMediumFree #10Cross-site request forgery (CSRF)Web securityMediumFree Unlock 60 more Web & Frontend questions · all 1,200 questions for $39/year (about 11¢ a day)See full access #11How does HTTPS work?Web securityMedium🔒#12Virtual DOM and reconciliationReactMedium🔒#14How does useEffect work?ReactMedium🔒#16Controlled vs uncontrolled inputsReactMedium🔒#18Making a website accessibleAccessibilityMedium🔒#22The critical rendering pathBrowser & performanceMedium🔒#23Reflow vs repaint (layout thrashing)Browser & performanceMedium🔒#24Core Web VitalsBrowser & performanceMedium🔒#26HTTP caching (Cache-Control, ETag)Storage & cachingMedium🔒#27Service workers and PWAsStorage & cachingMedium🔒#28WebSockets vs polling vs Server-Sent EventsHTTP & APIsMedium🔒#29Session cookies vs JWTsWeb securityMedium🔒#30How does "Sign in with Google" work?Web securityMedium🔒#31SSR vs CSR vs SSG (and ISR)ReactMedium🔒#33The rules of hooksReactMedium🔒#34useMemo and useCallbackReactMedium🔒#35Context vs Redux vs other state librariesState managementMedium🔒#36Making a slow React app fastReactMedium🔒#39Why isn't my z-index working?CSS Grid & positioningMedium🔒#42Organizing CSS at scale (BEM, CSS modules, Tailwind)Box modelMedium🔒#44Event bubbling and delegationDOM & eventsMedium🔒#45fetch and error handlingHTTP & APIsMedium🔒#47REST vs GraphQLHTTP & APIsMedium🔒#48Designing API paginationHTTP & APIsMedium🔒#49Idempotent APIs and retriesHTTP & APIsMedium🔒#51HTTP/1.1 vs HTTP/2 vs HTTP/3HTTP & APIsMedium🔒#52How DNS worksHTTP & APIsMedium🔒#54Content Security Policy (CSP)Web securityMedium🔒#56The same-origin policyWeb securityMedium🔒#57Storing passwords safelyWeb securityMedium🔒#58Rate limiting an APIWeb securityMedium🔒#59When and how to use ARIAAccessibilityMedium🔒#60Responsive and optimized imagesBrowser & performanceMedium🔒#61Loading web fonts without hurting performanceBrowser & performanceMedium🔒#62What is hydration?ReactMedium🔒#65Error boundariesReactMedium🔒#66Testing frontend codeReactMedium🔒#68requestAnimationFrameBrowser & performanceMedium🔒#69IntersectionObserverDOM & eventsMedium🔒#70Internationalization (i18n)HTMLMedium🔒#71Progressive enhancementHTMLMedium🔒#74Build a layout with CSS GridCSS Grid & positioningMedium🔒#76flex-grow, flex-shrink and flex-basisFlexboxMedium🔒#77CSS custom properties and dark modeResponsive designMedium🔒#79Implementing infinite scrollDOM & eventsMedium🔒#80Handling file uploadsFormsMedium🔒#81Web Components and the Shadow DOMDOM & eventsMedium🔒#83Cookie security attributesWeb securityMedium🔒#84HTTP security headersWeb securityMedium🔒#85How client-side routing worksBrowser & performanceMedium🔒#88Monitoring a frontend in productionBrowser & performanceMedium🔒#89Optimistic UI updatesState managementMedium🔒#90IndexedDB and offline dataStorage & cachingMedium🔒#94Keyboard navigation and focus managementAccessibilityMedium🔒#95Building an accessible modal dialogAccessibilityMedium🔒#96Performance budgetsBrowser & performanceMedium🔒#97Third-party scripts (analytics, ads, widgets)Web securityMedium🔒#98Walk me through a frontend you builtState managementMedium🔒#99script, async, defer and type=moduleBrowser & performanceMedium🔒#100A search box that doesn't spam the APIDOM & eventsMedium🔒