Web Performance Basics

A Brief Overview of Web Performance Management

Being Slow Can Be Worse Than Being Down

While availability is obviously critical to a successful enterprise on the web, the impact of slow page load performance is often underestimated. Performance affects the user perception of site quality, and not just at the moment in time when the user is trying to use your site. The effect of slow experiences persists into the future. Visitors who fail to load your site might be more forgiving and willing to try again in the future, whereas those whose experiences were bad may shy away from a return visit.

This is hard to appreciate fully.

We have, however, known of the importance of fast page loads for some time. As early as 2006, Google published a landmark study showing that 500 ms of delay reduced web searches by 25%. In 2009, Bing and Google published joint experiments that showed that as little as 200 ms of additional delay in page load times was enough to measurably change user engagement. 500 ms of additional delay was all it took to impact revenue on a commercial web site.

And nothing has really changed in the past decade. In 2013, Walmart revealed that every 100 ms improvement in page load time resulted in a 1% increase in revenue. In 2017, Akamai publishes biannual State of Online Retail Performance report that showed that a 100 ms delay in web site load time can hurt conversion rates by 7%. In 2018, Fashion retailer Missguided removed BazaarVoice for Android visitors; median page load time improved by 4 seconds, and revenue increased by 26%. There are dozens of other published studies and assessments showing the strong connection between web performance and business results, and a great resource to find them is

So You Need to Measure Performance

To fully understand how site performance is affecting your business, you need to take control with measurements to guide you. Web performance measurements give you a baseline to know where you are starting from. As you make changes to improve performance (or simply to add or change features on the site) you need to have a baseline to know whether the site is getting faster or slower. Web performance measurements also let you track changes over time. Even if you are not making major changes to the site design, it is important to track performance to ensure that users continue to get the same experience.

How we measure web performance also matters. Your measurements need to be as accurate and complete as possible. The measurements and the tools you use to visualize them should help you readily identify success and failure. It is not enough to know if the site has a 3 second median page load time, for example. You need to know that page load time is the correct metric for assessing the health of the online site, and whether 3 seconds is a successful or unsuccessful result.

The Ecosystem of Web Performance Measurement

Without getting into too much detail, web performance is commonly measured in four approaches today:

APM Short for Application Performance Monitoring, APM solutions help you assess the health and performance of the “nuts and bolts” of your infrastructure and application components. APM solutions primarily track events inside your own data center or in your own private cloud.

Synthetic This solution uses “agents” or “probes” to visit your web site robotically on a fixed schedule, measuring the performance from the (simulated) visitor’s point of view. Synthetic measurements may be scripted to complete multi-page transactions. Because each measurement is made using controlled variables (same locations, same browsers, etc.) they are great for probing for weaknesses and establishing benchmarks.

Web Analytics While many web analytics offerings include some performance measurement capability, these solutions are primarily aimed at categorizing and understanding your visitors and their behaviors on your site. Web analytics are popular because some of the basic offerings are free.

RUM Short for Real User Measurements, RUM solutions leverage JavaScript embedded on your web pages to query your visitors’ browsers for detailed performance information about the page load experience and send that information to a central repository through “beacons”. RUM offers the ability to get very comprehensive coverage up to 100% of all visitor experiences.

These four main approaches to web performance assessment are more complementary to each other than in direct competition. They each have their strengths and weaknesses. APM services offer less direct insight into overall visitor experience, and are generally unable to track performance of third-party or platform services on your pages. Synthetic measurements offer no insight into visitor engagement, and no insight into conversion and revenue. Web analytics offers only very light, to no, insights into performance. Real User Measurement services collect data sets that can be extremely large, the data can be noisy with many outliers, and distilling this data into business intelligence can be a challenge.

All of that said, Real User Measurements offer some significant benefits. You should think of them as the “ground truth” for visitor experience. They are not simulating real-world conditions or looking at a limited portion of the user experience. These measurement come directly from your visitors’ own browsers. RUM measurements will covers all variety of site visitors (across geography, device type, connection type). The stronger recommendation for RUM, however, is that it can captures both performance and business metric data at the same time. Knowing what the user experience was like when they complete a purchase or choose to view an another article, and what it was like if they did not, is key to making good business decisions about site performance.