Conversions: Faster Mobile Sites, More Revenue

by Luke Wroblewski March 24, 2017

In his Faster Mobile Sites, More Revenue presentation at Google Conversions 2017 in Dublin, Ireland, Guillaume Derolez shared a number of ways to optimize the loading time of mobile Web pages. Here's my notes from his talk:

  • Smartphones are performance constrained but users have high expectations of performance.
  • Mobile commerce is an upper funnel affair: customers have a 50% chance to engage with your brand on mobile first.
  • Most conversions touch 2.6 devices.
  • The average load time on mobile commerce sites is 7 seconds for US retail mSites.
  • As page load time goes from: 1s to 3s the probability of bounce increases 32%
  • Mobile pages that load 1s faster see up to 27% increase in conversions.
  • So how fast should mobile pages be? The target for page loading is one second but on a 3G connection, 600ms is needed for overhead which really leaves you with 400ms for round-trip server connection.
  • Top three areas to investigate in order to make mobile Web pages faster: images, non-minified resources, number of requests.
  • Images: 67% of bytes in the average Web pages are images; can be compressed to save bytes. Use lazy loading: only load what is needed for visible on screen elements, later load rest. Avoid “download and hide” or “download and shrink”.
  • Non-minified resources: CSS & JS can be compressed to save 70% of transfer sizes. Enable GZIP. Minify the files.
  • 68% of Websites on Web load more than 50 resources. To limit requests: make use of browser cache, consolidate page resources, load javascript asynchronously, prioritize above the fold CSS.
  • Too many redirects: DNS lookup + connection + data together take time for each redirect.
  • Mobile site speed should be considered a profitable site feature.