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Who's Afraid of the Big Bad Preloader?

Yoav Weiss (Akamai)
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(3.78, 18 ratings)
Slides:   external link

The preloader is an essential performance optimization mechanism that exists across all modern browsers, yet it remains a mystery to many Web developers.

The responsive images debate has put a light on the tension between the Web developer’s need for control over resource download and the browser’s need to download required resources as soon as possible, with the preloader being in the center of controversy. Fortunately, better understanding of the browser’s fetching mechanisms and newer APIs that provide the developer with more control can bridge this perceived gap.

In this talk we will:

  • Overview what the preloader does and doesn’t do
  • See the difference between preloaders of different browsers
  • Debunk the myths surrounding it
  • See how developers can make their sites “preloader-frienly”, and how they can avoid resource preloading, if they really must
  • See how the preloader can be further improved in the future
Photo of Yoav Weiss

Yoav Weiss


Yoav is a Web performance and browser internals specialist, working on responsive design Web performance, image compression and more. He recently implemented the srcset attribute in Blink.

He is an
RICG technical lead, a Blink & WebKit contributor and a bass player.

You can follow his rants on Twitter or have a peek at his latest prototypes on Github.