dns-prefetch + preconnect vs. browser cache
问题 To improve the page load time I want to use dns-prefetch and preconnect for external javascripts. <link rel="dns-prefetch" href="https://example.com"> <link rel="preconnect" href="https://example.com"> What happen if the ressource (in my case the external javascript) is already in the browser cache? Do dns-prefetch and preconnect add page load time unnecessarily? In other words: Are dns-prefetch and preconnect only useful on the first page load? 回答1: On the repeat visit, the preconnect/dns