The technique used if fairly simple: Instant.page calculates the time a user spends hovering a link (which is an obvious behavior when you want to click on something) and will start preloadind said link if that time exceeds 65ms. Since the average human perceives actions taking less than 100ms as instantaneous, Instant.page tricks the brain, hence allowing your users to get a faster, better experience.
The installation is fairly simple, just insert the
<script> tag containing the link to the script right before the closing
</body> of your website (which is where all your scripts should reside anyways), and you're all set! Instant.page will glue itself automatically to each link on the page. The library is small, a mere 1kB. It's free and open source (MIT).
Instant.page allows you to control what content should be preloaded or not. You might want to prevent it from preloading some anchors, like logout links for instance. To do that, simply add a
data-no-instant attribute to said links and Instant.page will ignore them. You can even specify that you want to allow preloading for external links.
Simple, light and easy. If you want to try it yourself, check out Instant.page here: https://instant.page