Rendering

The Preload Scanner

A secondary parser that races ahead of the main one while it's blocked, spotting and pre-fetching resources — images, scripts, stylesheets — before they're formally reached.

Images lower in the page start downloading before the parser gets there.

HTML
⏸ scriptimgcssjs
Prefetch
Parser blocked; scanner fetches ahead
A second parser races ahead

Tap the example to replay it · press and hold to slow it down

One of 40 cards in javascript flashcards. Browse every card.