Step 3: Multiple DNS Lookups Issue

The Problem

When loading images from multiple domains, the browser needs to perform a DNS lookup for each unique domain. This can significantly slow down the initial page load.

Performance Impact:

  • Multiple DNS resolutions (check Network tab)
  • Additional TCP connections
  • Increased latency
  • More SSL handshakes

Problematic Code:


// Images coming from different domains
"https://images1.example.com/image1.jpg"
"https://cdn2.different-domain.com/image2.jpg"
"https://static.another-server.net/image3.jpg"
"https://media.different-host.com/image4.jpg"
// ... and so on

Open Chrome DevTools (Network tab) and check the number of unique domains being accessed. Each requires a separate DNS lookup. To simulate a fresh DNS lookup, clear the DNS cache by navigating to chrome://net-internals/#dns and clicking on Clear host cache.

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