A retailer's guide to web performance
I’m at Shop.org this week, having really interesting conversations with online retailers. What I love about talking with this crowd is that – like me – they're super focused on user-perceived performance. Not surprisingly, we have a lot to talk about.
Making customers happy is the not-so-secret secret to retail success. Delivering a fast, consistent online experience has been proven to measurably increase every metric retailers care about – from conversions and revenue to retention and brand perception. (In fact, there's so much research in this area, I dedicated an entire chapter in my book to it. You can also find a number of great studies on WPO Stats.)
Delivering great, fast online experiences starts with asking two questions:
- What’s making my pages seem slower for my users?
- What can I do about it?
The good news is that most of the issues that are making pages slow for your shoppers are right on your pages, which means you have control over them. Here's an overview of the most common performance issues on retail sites, and how you can track them down and fix them.
Woohoo! I'm helping build SpeedCurve
I’m super excited to be able to say that I’ve joined Mark, Steve, and Tammy at SpeedCurve!
I’ve watched how Mark has shown over the last couple of years that performance monitoring doesn’t have to be dry and data-heavy; it can be insightful, interactive, and actionable. I’ve also been a follower of Steve’s work for many years. In fact, I should probably thank Steve for providing me with the knowledge that got me interested in web performance in the first place! Tammy’s work has been really interesting to follow, too - her focus on real people and how web performance impacts the way they use our websites is something that resonates strongly with me.
Joseph making BBC News way faster for all users.
Waterfall with browser events
We've improved our already fantastic interactive waterfall chart with a new collapsed mode that highlights all the key browser events. This lets you quickly scan all the events that happen as the page loads and if you scrub your mouse across the waterfall you can easily correlate each event to what the user could see at that moment.
Along with all the browser metrics you also get to see our new hero rendering times in context. Click on any event to see a large version of that moment in the filmstrip.
Hero Rendering Times: New metrics for measuring UX
The key to a good user experience is quickly delivering the content your visitors care about the most. This is easy to say, but tricky to do. Every site has unique content and user engagement goals, which is why measuring how fast critical content renders has historically been a challenging task.
That's why we're very excited to introduce Hero Rendering Times, a set of new metrics for measuring the user experience. Hero Times measure when a page's most important content finishes rendering in the browser. These metrics are available right now to SpeedCurve users.
More on how Hero Rendering Times work further down in this post. But first, I want to give a bit of back story that explains how we got to here.
The average web page is 3MB. How much should we care?
See our more recent page growth posts:
- What is page bloat? And how is it hurting your business, search rank, and users? (July 2023)
- 10 years of page bloat: What have we learned? (March 2022)
A couple of month ago, someone asked if I'd written a page bloat update recently. The answer was no. I've written a lot of posts about page bloat, starting way back in 2012, when the average page hit 1MB. To my mind, the topic had been well covered. We know that the general trend is that pages are getting bigger at a fairly consistent rate of growth. It didn't feel like there was much new territory to cover.
Also: it felt like Ilya Grigorik dropped the mic on the page bloat conversation with this awesome post, where he illustrated why the "average page" is a myth. Among the many things Ilya observed after analyzing HTTP Archive data for desktop sites, when you have outliers that weigh in at 30MB+ and more than 90% of your pages are under 5MB, an "average page size" of 2227KB (back in 2016) doesn't mean much.
The mic dropped. We all stared at it on the floor for a while, then wandered away. And now I want to propose we wander back. Why? Because the average page is now 3MB in size, and this seems like a good time to pause, check our assumptions, and ask ourselves:
Is there any reason to care about page size as a performance metric? And if we don't consider page size a meaningful metric, then what should we care about?
Find and fix what matters most
Being able to monitor and measure the performance of your pages is crucial. You know that already. You also know that the next step is to quickly find out what’s hurting your pages so you can stop the pain.
You want to know:
- Which performance rules is my page breaking?
- How do I prioritize my optimization efforts?
- How can I communicate this quickly and clearly to my team?
We’re super excited to announce that you can now use SpeedCurve to answer these questions.
I've joined SpeedCurve! Here's why
TL;DR
If Mark and Steve invited you to work with them, what would you say? Exactly.
Long version
Okay, I have to elaborate a bit more about why I’m ridiculously excited about working with Mark and Steve. My first foray into the performance space was at the Velocity Conference in 2009. If you had told me then that someday I’d be working with that tall guy rocking the main stage, I would’ve thanked you for the kind words… while secretly thinking you were nuts. But here I am!
Tammy at International Women's Day Tech Talks in Toronto
A/B Testing JSONP and the Preloader with RUM
SpeedCurve is a SPA (Single Page App) so we construct the charts dynamically using JSONP. It works great, but we're always looking for ways to make the dashboards faster. One downside to making requests dynamically is that the browser preloader isn't used. This isn't a factor for later SPA requests, but on the first page view the preloader might still bring some benefits. Or maybe not. We weren't sure, so we ran an A/B test. Long story short, doing the first JSONP request via markup caused charts to render 300 milliseconds faster.
Improved Favorites
We've improved the "Favorites" dashboard which now lets you build your own charts which:
- Combine synthetic tests and LUX (real user monitoring) in one chart.
- Choose average, median, or 95th percentile.
- Create charts that have multiple metrics.
- Select multiple values for a filter, eg, browser = Chrome or Firefox, country = UK or US.
- Compare A/B tests in a single chart.
Here's a walkthrough showing you some of the new features:
Measuring Blocking Resources
SpeedCurve reports the number of critical blocking resources in the page. These are the resources that block rendering. Since it's important that users see your content as quickly as possible, it's important to know what might be causing your page to render slowly. We recently enhanced the way we measure blocking resources and wanted to share those improvements with our customers as well as the performance community at large.
The main culprits that block rendering are scripts and stylesheets that are loaded synchronously. A great way to avoid this blocking problem is to load your scripts and stylesheets asynchronously. You can do that for scripts by using the async and defer attributes, plus other programmatic techniques. Loading stylesheets asynchronously is less popular but is still possible using techniques like loadCSS.
