title: What are the differences between html preload and prefetch?
body: <p>Preload and prefetch are both used to request resources in advance so that later resource loading can be quick. It seems that I can interchange the two</p>
  
  <p><code>&lt;link rel="preload" href="foo.js" as="script"&gt;</code></p>
  
  <p><code>&lt;link rel="prefetch" href="foo.js"&gt;</code></p>
  
  <p>without noticing anything difference.</p>
  
  <p>What are their differences?</p>