Web Dev Interview Questions

What is a REST API?

A REST API is a web interface that exposes data as resources identified by URLs, which clients manipulate using standard HTTP methods (GET, POST, PUT, PATCH, D…

Cookies vs Sessions vs JWT

A cookie is a small piece of data the browser stores and sends back with each request; a session keeps user state on the server and uses a cookie holding only…

What is CORS?

CORS (Cross-Origin Resource Sharing) is a browser security mechanism that lets a server explicitly permit web pages from one origin to make requests to a diffe…

Difference Between GET and POST

GET retrieves data and puts its parameters in the URL query string, making it idempotent, cacheable, and safe (no side effects), while POST submits data in the…

REST vs GraphQL: What Is the Difference?

REST exposes fixed, resource-shaped endpoints where the server decides what each response contains, while GraphQL exposes a single endpoint with a typed schema…

What Is OAuth?

OAuth is an authorization framework that lets a user grant a third-party application limited access to their resources on another service, without ever sharing…

What Is the Virtual DOM?

The virtual DOM is an in-memory, lightweight JavaScript representation of the real DOM that frameworks like React use to compute the minimal set of changes nee…

What Is Web Caching?

Web caching is the practice of storing copies of responses — HTML, assets, or API data — at various points between origin server and client so that repeat requ…

What Is Webpack and Bundling?

Webpack is a module bundler that walks a JavaScript application’s dependency graph starting from an entry file and combines all the modules, along with assets…

Server-Side vs Client-Side Rendering

Server-side rendering (SSR) builds the full HTML for a page on the server and sends it ready to display, while client-side rendering (CSR) sends a near-empty H…

What is a WebSocket?

A WebSocket is a communication protocol that opens a single, persistent, full-duplex connection between client and server over TCP, letting either side send me…

What is the Same-Origin Policy?

The Same-Origin Policy (SOP) is a browser security rule that restricts scripts on one origin (scheme, host, and port) from reading data from a different origin…

What is CSRF?

CSRF (Cross-Site Request Forgery) is an attack where a malicious site tricks a victim's browser into sending an authenticated request to another site the victi…

What is XSS?

XSS (Cross-Site Scripting) is a vulnerability where an attacker injects malicious JavaScript into a page viewed by other users, letting that script run with th…

What is a Single-Page Application?

A single-page application (SPA) loads one HTML shell up front and then rewrites the page in the browser with JavaScript, fetching only data — not full new page…

What is Lazy Loading?

Lazy loading is the technique of deferring the loading of a resource — an image, a script chunk, or a component — until it is actually needed, instead of loadi…

What is a Service Worker?

A service worker is a background JavaScript script the browser runs separately from the page, letting it intercept network requests, cache responses, and enabl…

What is Content Security Policy (CSP)?

Content Security Policy (CSP) is an HTTP response header that tells the browser which sources of scripts, styles, images, and other resources are allowed to lo…

What are HTTP Caching Headers?

HTTP caching headers are response headers such as Cache-Control, ETag, and Last-Modified that tell browsers and intermediate caches how long a response can be…

Debouncing vs Throttling

Debouncing delays running a function until a burst of calls stops for a set pause, so it fires once at the end, while throttling runs the function at most once…

What is the DOM?

The DOM (Document Object Model) is a tree-structured, in-memory representation of an HTML or XML document that browsers build from parsed markup, letting JavaS…

What is Progressive Enhancement?

Progressive enhancement is a design strategy that starts with a basic, functional HTML experience for every user and browser, then layers on CSS and JavaScript…

What is an HTTP Status Code?

An HTTP status code is a three-digit number returned by a server in every HTTP response, grouped by its first digit into a class (1xx informational, 2xx succes…

What is API Versioning?

API versioning is the practice of labeling breaking changes to an API with a distinct version identifier — in the URL, a header, or a query parameter — so exis…