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Frontend Academy · Lesson

Browsers DNS and HTTP: The Request Lifecycle

Follow a URL from the address bar through DNS resolution, TCP connection, HTTP request, and server response back to the browser.

What Happens When You Type a URL?

Every time you visit a website, your browser kicks off a precise sequence of steps. Understanding this sequence makes you a better developer — you know where things can go wrong and how to speed them up.

Step 1 — DNS Resolution

DNS (Domain Name System) is the phone book of the internet. Your browser asks a DNS resolver: "What IP address is behind example.com?". The resolver checks caches and, if needed, queries authoritative name servers.

# DNS lookup chain
# Browser cache → OS cache → Router cache → ISP resolver → Root NS → TLD NS → Authoritative NS

All lessons in this course

  1. Browsers DNS and HTTP: The Request Lifecycle
  2. HTML CSS and JavaScript: Each Layer's Job
  3. How a Page Renders: Parsing DOM CSSOM Layout Paint
  4. Developer Tools: Opening and Using DevTools
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