How video impacts mobile web performance and UX, part 1: data and download speed

By Andy Favell

Graph shows the growth of mobile data, and the increasing share of mobile video (as described in the text).

Mobile video is great. When it works.

Implemented correctly, video or audio *should not* impact the speed that pages load on a mobile device and when the play button is pressed, it needs to start quickly and work well.

Video content is top of the agenda for many brands. It is proving a great way to engage customers and visitors, but when viewed on mobile devices, particularly those on cellular connection, video (and to a lesser extent audio) should come with a health warning.

Users are increasingly impatient with slow-to-load and stalling video and will start to abandon a video after waiting just two seconds, research from UMass and Akamai shows.

This column, the first of three parts, will take a close look at how and why video affects page performance. In the second part, we’ll look at the impact of video autoplay and audio on page performance, as well as what makes a poor viewer experience (VX).

Finally, we’ll explore how to detect, avoid and remedy issues to prevent users tuning out.

Video is a massive mobile data hog

The provision and consumption of video on mobile devices via web and apps is growing rapidly. Mobile video is already 60% of total mobile data traffic worldwide and is expected to be 78% by 2021 according to Cisco’s Visual Networking Index (VNI).

All other elements will grow over the next five years, but their proportion of overall traffic will be less. Audio will be 5% compared with 8% today and mobile web will be 14% compared with 30% of traffic today.

Video – and audio – used wrongly or inefficiently will impact mobile user experience (UX) – or should we say: “viewer experience” (VX) or “listener experience” (LX) – massively, but not necessarily in the same way as oversized images and poor or inefficient use of JavaScript.

Images and JavaScript, as seen in previous columns, are the biggest causes of slow loading mobile web pages. As discussed below, video can still contribute to page size and therefore contribute to page load delays, particularly (it seems) where autoplay is used, as we will discuss below.

But the biggest impact on VX comes after page load when the video is slow, or fails, to start or stalls.

The two charts below are from HTTP Archive, which twice monthly records the page size and download speed of the homepages of the top 1 million sites to desktop and mobile devices, using the excellent WebPageTest.

The first chart shows the breakdown of content types by bytes – images, JavaScript, video, stylesheets, HTML and fonts – as an average of all homepages recorded on April 15, 2017.

Video is 128kB or 5.5% of the total bytes loaded (2312 kB or 2.3MB). This might appear small, until you realize that 97% of pages monitored by HTTP Archive have no video content (we examine this surprising stat below).

Pages that do have video content will therefore show a higher proportion of video content.

The second chart (captured April 15, 2017) shows the content breakdown for the homepage Go to the full article.

Source:: Search Engine Watch