Speeding up 3rd party widgets using ASWIFT

This is a summary of the talk by Arvind Jain, Michael Kleber from Google at velocityconf about how to write widgets using same domain iframe using document.write. Speed improvements of over 90% in loading widgets with this change.

  • Web is slow
    • Avg page load time 4.9s
    • 44 resources, 7 dns requests, 320kb
    • Lot of 3rd party widgets
      • digg/facebook/etc
  • Measurements of 3rd party widgets
    • Digg widget
      • 9 HTTP requests, 52 kB
      • scripts block the main page from downloading
      • stylesheets blocks the main page from rendering in IE
    • Adsense takes up  12.8% page load time
    • Analytics takes up < 5%   ( move to async widget )
    • Doubleclick takes up 11%
  • How to make Google AdSense “fast by default”
    • Goals / Challenges
      • Minimize blocking the publishers page
      • Show the ad right where the code is inserted
      • Must run in publishers Domain
    • Solution (ASWIFT) – Asynchronous Script Written into IFrame Tag
      • Make show_ads.js a tiny loader script
      • Loader creates a same-domain iframe (using document.write)
      • Loads the rest of the show_ads into the iframe by document.write() of a <script> tag
      • This loading of iframe is asynchronous.
    • Browser specific surprises
      • Problems with parallel downloads of same script in IE
      • Iframe creation inside <head> in Firefox has a problem
      • Requesting headers in Chrome was buggy
      • Forward-Back-Reload behavior is buggy (refetching instead of using cache)
      • document.domain vs friendly iframes

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