This article was
originally published on the SiteSpect site. It has been revised slightly for TechRepublic.
Mobile devices represent a significant, and growing, portion of all
Internet traffic (15% according to the latest Mary Meeker Internet Trends report). Clearly, having a mobile site is important, but it also has
to be fast and functional in order to deliver the best and most enjoyable user
So, what are some of the most common performance issues slowing down
- Making too many HTTP
requests. Connection time and latency are two of the primary factors in
mobile site performance and are directly related to the number of
requests. As the number of HTTP requests made for different components
(images, scripts, stylesheets, etc.) increases, so does the time it takes
for the website to load on a mobile device.
- Images are large and
not optimized for the screen size of the visitor’s device. Larger images
generally mean larger file sizes. As a result, the mobile browser will
take more time to display images properly. Images should be served based
on the visitor’s device type, and should be appropriately sized to that
device’s screen size. Compression of images is naturally important to both
the web and mobile, especially when a mobile device is using a 3G or 4G
- Redirects take up
valuable loading time. According to Nicholas Zakaz of Yahoo!, redirects consume 40% of the time to load a page. Client-side redirects that
to render on the visitor’s browser, and then redirect to the new page and
load within the browser all over again.
inhibits performance. As Bryan McQuade of Google’s Page Speed team
the <head>) are performance killers, and they are especially
expensive on mobile due to the higher round trip times associated with
- Loading the entire
page takes time and creates a poor user experience. Loading the entire
page of a mobile site can consume a significant amount of extra time and
increase the number of requests that make the overall user experience
poor. For example, if you have an image gallery on the lower section of a
page and a smartphone visitor will not immediately see the gallery on
their device, it will still cause everything else on the page to load more
slowly as a result of the whole page loading at the same time.
There are a number of best practices for mobile optimization to address
each of these five challenges and to ensure your mobile site is loading as
quickly as possible. The end goal should be to load the mobile version of a
page in one second, as that is when visitors begin to lose attention to your site. To get started, measure your mobile
site performance, and then jump into the list of suggestions below to reduce
mobile response times as close to one second as possible.
- Remove HTTP requests. This is crucial for
mobile web performance, but how do you remove these requests without
removing features and functionality? Image spriting is one example that
removes individual HTTP requests as a result of concatenating images into
recommend A/B testing these optimizations, as they will have different
impact on different pages, browsers, and devices. Then segment by device
and look at the impact of testing by device and browser types on your
optimizations to really focus on specific performance improvements for
core segments of your audience.
- Reduce image size by
compressing images and
ensure you are using the optimal web format. Some common formats that
generally produce small image sizes are JPG, PNG, and, in certain cases,
GIF. In addition, mobile versions of the Chrome and Firefox browsers
support a new image format called WebP that generally has much smaller
- Use server-side
redirects to make page changes more efficient for the end-user. This may
require changes to your URL structure and should be discussed with
internal IT personnel before any changes are made.
- Minimize the amount
asynchronously so that the browser will not be blocked from processing
to the desktop version of your site on your mobile pages, be sure to
- Load content that the user will see “above the fold” right away.
Lazy-load any additional content until needed. For example, for an image
gallery, you may be able to load the current, previous, and next images
only and then lazy-load remaining images to optimize performance. In
addition, there are many cases where you can use CSS3 instead of images.
Take into account these best practices as you
optimize your mobile site and, more importantly, A/B test each change to obtain
a data-driven understanding of what works for your visitors. Real User
Monitoring (RUM) metrics will allow you to measure crucial time-based
information such as the amount of time a visitor stays on your mobile page.
Jeffrey Vocell is the
Product Marketing Manager for SiteSpect, where he’s responsible for strategy and communication of product
messaging. Prior to SiteSpect, Vocell co-founded Trendslide, a mobile business
analytics startup. He holds a B.S. in Business Management and Leadership from
Daniel Webster College.