Intechnica recently did some in-depth research into how the performance of ecommerce (specifically fashion retail) websites is being affected by the over-proliferation of third party content, the results of which have been published in our brand new report, “The Impact of Third Party Content on Retail Web Performance”.
For the uninitiated, third party content refers to basically anything on your website served externally – usually adverts, tracking tags, analytics codes, social buttons and so forth. Check here and here for some good background on the dangers of third party content.
If you are already initiated, though, you will already know that this content places an overhead on a website’s performance to varying degrees. In a best case scenario you’re looking at some extra page weight in the form of objects, which are being served from added hosts via extra connections to your users, the result being a few extra milliseconds on your page load time. On the other end of the spectrum, a misbehaving piece of third party content can slow pages to a crawl or even knock your site offline. Remember when everyone blamed Facebook for taking sites like the Huffington Post, Soundcloud and CNN down? Yep. Third party content at its most disruptive.
So what did we want to find out?
We wanted to really see how much of an impact third party content was having on real websites. We went about this by doing some external performance monitoring of the normal websites in parallel with filtering out the third party content (which we identified based on experience – if you want to see an open source, ever-growing list of third party content, I recommend ThirdPartyContent.org). It’s also important to note that we measured a “land and search” transactional journey, not just home page response, to get a more realistic measurement. From this information, we were able to distinguish which kinds of content are most prevalent and even what element of this content was most to blame for any performance overhead. It also gave us some interesting insights into whether sites that use third party content more conservatively also happen to follow other web performance best practices.
Some fast facts
There is more detailed data in the report itself, which is available to download in full here. However, let’s look at some key findings. Keep in mind that some of these might seem predictable but it’s nice to have some concrete data, isn’t it?
- In general, sites that use more third party content are heavier, use more hosts and connections, and are slower than those that use less third party content.
- When third party content is completely filtered out, websites with a lot to begin with see a greater immediate speed boost than those with less to begin with. In fact, many retailers swapped places in the rankings once third party content was taken out of the equation.
- Falling in line with the famous “golden rule of web performance”, it’s the extra hosts, connections and objects brought on by third party content that result in slower response times – more so, in fact, than page weight.
Some pretty graphs and tables
I recently saw someone on Twitter express the rule “nt;dr” (no table; didn’t read), so let’s get some data in this post, shall we?
The chart above shows the average number of each type of third party content present on each of our target websites. As you can see, there is far more variation in adverts than in any other form of third party content, although it’s somewhat surprising to see the average of 1.8 analytic tags on these websites. Serving adverts etc. from multiple hosts impacts performance, as we see in the table below…
Our second table tells us a little more about why sites with more third party content tend to be slower. The median, maximum and minimum response, hosts ,connections, objects and size represent only what is added to the sites by third party content, not the overall metrics. We can see that third party content alone is adding up to 18.7 seconds to the response time (a median of 9.4 seconds). What’s also interesting is that there is a stronger correlation between average response time and number of objects, connections and hosts added than there is between response time and added page weight (0 is no correlation ,1 is absolute correlation).
The last chart I’ll show you here is very telling in terms of real impact of third party content. Red and blue are the full, normally served websites of Retailer A and Retailer B respectively. We can see that red is much slower than blue during this time period. Yellow and green are the same websites (A and B respectively) except with all third party content removed. Not only did Retailer A gain a greater speed boost than Retailer B by filtering this content out, but it actually went from being the slower website to being the faster of the two. What’s even more interesting is that Retailer A reported disappointing revenues of this period, while Retailer B posted a strong revenue report.
Read the full report
This is just a sample of some of the data we collected and analysed, so make the jump to our website to read the full report for yourself.