Web

How the web works: client and server, HTTP, browser rendering, performance, storage and security.

1. 1How the web worksClient, server, DNS, URL and origin — what happens when you open a page.
2. 2HTTP: methods, statuses, headersThe language between browser and server, HTTP caching and what idempotent means.
3. 3How the browser rendersDOM, CSSOM, layout, paint, composite and Core Web Vitals.
4. 4Web performanceCore Web Vitals, lab vs field data, the common causes and their fixes.
5. 5Image optimizationFormat, size, compression, lazy vs priority, reserved space and next/image.
6. 6Cookies, localStorage, sessionStorageThe 5 places the browser keeps data and when to use each.
7. 7Security: XSS, CSRF, CORSThe same-origin policy and the 4 attacks every frontend developer must know.