Images and Third Party Content Impact Mobile Site Speed

By Dan Galatin, Mobile Web Performance Evangelist, Keynote | July 09, 2014

This month we took a look at the special mobile version of the Keynote US Lodging and Travel Index, exclusively created for Hospitality Technology. While guests tend to book stays from their desks at home when planning travel, smartphones are overwhelmingly used for same day bookings. Getting your mobile site right is key to converting these same day guests! But, the mobile world offers challenges around delivering content without impacting performance. We looked at the impact of CDNs, for example, in April, as one way to help deliver quality content without slowing performance.
This time we examined two sites – Wyndham Worldwide and Accor Hotels - to compare the amount of page elements versus page size and the effects these differences had.
Wyndham has a slightly larger site compared to Accor Hotels, but is actually faster – by a significant eight seconds across a local area network and over 14 seconds on cellular networks - in load time. How do they do it? Far fewer page elements – such as images or third party links.
On average Wyndham has 40 elements compared to Accor’s 186. Wyndham loads 25 image files while Accor loads 82. These two categories make a big difference over mobile networks, where time and latency have a major impact on performance.
We see Wyndham initiate 20 connections in loading its homepage while Accor initiates 67. We’ve mentioned this before – each of these connections requires “fetching” which takes a dramatic turn on mobile sites.
How to get around this on the sensitive mobile sites? We recommend combining images smaller than 2Kbytes using CSS Sprites. This turns them into one, much more manageable, image file. For JavaScript, the best practice is to have them load last whenever possible so they have minimal impact on rendering.
A similar category is the third party content. Wyndham loads content from two domains while Accor racks up 43! Beyond the usual ones such as Google Analytics and Facebook we see Pinterest, Twitter and a TripAdvisor logo. Just as with JavaScript, make sure these third parties aren’t slowing down the load and have them render later so they don’t impact initial load time. Better still, cut the number of third party domains down to a more manageable number.
These two sites offer some great examples of how size doesn’t always have to be a drag on mobile sites – despite everything we say about keeping them light. You can in fact optimize content so even with a larger sized site, performance isn’t dramatically impacted for the worse.   
View the Keynote US Lodging Performance Index – for Desktop Sites here.
Anyone can also sign up for a free weekly email delivery of the Index. Use it to track how your company’s performance is doing against the competition, or just to follow what some of the major names are setting as performance standards. Keynote runs a large number of US and global Indexes, across a range of industries and government, which many organizations use as the benchmark to achieve their own optimum Web performance.

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