Over the years various researchers and organizations have released tons of stats and case studies that correlate site latency with diminished revenue. The question no longer is “does performance matter?” Instead, the question is has become “how do I make my website faster?”
I have written a few blogs detailing technologies and techniques that retailers can use to improve the performance of their websites and web applications. Today, I want to address a very specific problem that will solve, or at least drastically improve, poor performance for 90% of retailers: unoptimized images.
Are images really the issue?
The above graph is from HTTP Archive (an awesome resource for analyzing web performance trends over the past 5 years) and shows the average page size of over 3,500 websites since November 2011.
In November 2011, the average website was just under 1 MB in size (929 KB) and now the average webpage is over 2 MB (2167 KB). That’s a 233% increase in just four years!
Ok, so we’ve established that the web has gotten a lot larger, but that doesn’t necessarily mean that images are to blame. After all, the web as a whole has gotten a lot more complicated in recent years, right?
This graph shows the weight of image files loaded during the same timeframe as above for the same sample of websites. We see that the average website in November loaded roughly .5 MB of images (577 KB) and today the average website loads nearly 1.5 MB (1370 KB) of images. This is roughly a 237% increase over the four year timeframe.
This actually isn’t very surprising because image weight has grown at about the same rate as the overall web page. In fact, the ratio of images to all other content on a typical website has only increased by about 1% over the last four years. Not much of an increase.
The unbelievable part is that the number of image requests made over the past 4 years has remained unchanged. The average webpage today requests around 55 images, which is the same number of image requests made 4 years ago. What does all this mean? (Other than the CDN industry is raking in the money…)
It means that while websites today are using the same amount of images, the average size of those images has grown by over 200%!
To illustrate the growth of images, we used Zoompf to scan Sharpie’s eCommerce store for North America. Our scan found that the homepage for their storefront is 6.2 MB. That is 300% bigger than the average website and roughly the size of an ebook (or 2 MP3’s)!
Of the 6.2 MB total, 61% (3.8 MB) of the page weight is attributable to images. If these images were properly optimized using a variety of techniques, Sharpie could reduce the weight of this page by 3.5 MB (93%) without noticeably lowering the graphical quality of the images.
The above background image is a great example to illustrate what we can optimize on this page. Right now this image accounts for 665 KB of page weight. Its post optimization size? 44KB. If you care to take a deeper look at the scan above, feel free to check it out.
Unoptimized images and media affect more than just the user experience by slowing page load. They also directly impact your costs with CDNs and can exponentially increase the load on your servers during peak periods like Black Friday where organic traffic can spike over 800%.
What can you do?
If you are interested in optimizing all of your media in preparation for the holiday season, check out our Free Holiday Trial. We’ll give you a prioritized list of media files that are slowing your user experience, as well as the optimized version of those files for your team to upload on your site.
You can also check out this great presentation, Achieving Better Image Optimization, by Billy Hoffman for tips on optimizing your images.