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Web Performance News, December 2019

Photo by Jeremy McKnight on Unsplash
  • This one is a biggie — Safari now supports Intersection Observer! Intersection Observer is a relatively new Web API for lazy loading content on the page. At Pixboost we are using it in our pixboost.js and pixboost-react libraries. My biggest problem with Intersection Observer was a polyfill that is quite buggy and most of the time we preferred to not use lazy loading at all if Intersection Observer was not available on the browser.
  • Safari has just implemented Intersection Observer API, but there is a new version of spec coming: https://developers.google.com/web/updates/2019/02/intersectionobserver-v2. The latest version is not a full rewrite, but adding some additional functionality to better track visibility of the elements.
  • Chrome is implementing a change to calculate image dimensions before loading it so that page layout won’t be affected. Worth to mention that Firefox already has this upgrade. To be ready just add width and height attributes to your <img> and <video> elements. Google Group discussion and explanation from @jensimmons:
  • In case you missed it, Google is using page speed as a ranking factor on the mobile search since 2018. Here is a quick summary of how that decision influenced the Web so far.



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Dmitry Pokidov

I’m a CTO of pixboost.com — boosting performance and conversion of your online store.