browser prefetch and performance

browser prefetch and performance.txt

Resolve DNS

<link rel="dns-prefetch" href="//example.com">

Resolve DNS and also make the TCP handshake and optional TLS negotiation

<link rel="preconnect" href="http://css-tricks.com">

Fetch and store in cache, Definitely for webfont

<link rel="prefetch" href="image.png">

Same as prefetch, but greater priority than prefetch. So this will be loaded earlier than prefetch

<link rel="subresource" href="styles.css">

Load all resources and render full page in memory, so if user on visit will be shown a superfast cached page. 

<link rel="prerender" href="http://css-tricks.com">

Same as prefetch, but prefetch can be ignored by browser (like for large file..), but preload will always be executed. 
Not supported by current browsers

<link rel="preload" href="image.png">


More details at : https://css-tricks.com/prefetching-preloading-prebrowsing/