A flawed approach to page speed measurement is sabotaging ecommerce sites. There, I said it.
Now I know this might be an exaggeration, but it really is time for a change. A historical focus on network-based metrics — bytes downloaded per page or assets per page, for example — and an excessive emphasis placed on first-page load times have meant the rest of the customer journey on the web has suffered.
Developers and product managers have been relying on tools like Google’s Lighthouse to measure page load speed, and once the search giant began considering mobile page speeds in its website ranking algorithm, that reliance only grew.
Unfortunately, while Lighthouse and similar tools are great for measuring first-page loads, they don’t measure browsing speed — the time it takes to transition from one page to the next. That’s a glaring omission.
We build what we measure
Mobile UX expert Luke Wroblewski has summed the problem up nicely: “People unlock their phones around 80 times a day. … Most sessions are very short — most under 30 seconds. Given that, if things are slow, you’re going to really, really, really hate it.”
In fact, Ericsson researchers have determined that slow loading times create the same psychological discomfort for users as watching a horror movie or waiting in line at a store. The latter is especially telling, as consumers often turn to mobile shopping precisely to avoid those long lines. Yet, according to Monetate data, typical mobile sites convert at only 38 percent of their desktop counterparts. Optimizing mobile browsing speed will help close this gap.
This issue affects ecommerce websites in particular because the average ecommerce session is just over three minutes long and covers six pages, each taking almost seven seconds to load. That means for 20 percent of the session, users are waiting, bored. Shaving a second off the first-page load doesn’t drop the wait time much, but reducing browsing speed to the sub-second range (e.g., 300 milliseconds) brings the time spent waiting (and NOT engaging) down to just 5 percent.
As a user, that certainly makes for a better experience. On the other side of the screen, the only way to evaluate whether a website has horror-film-like effects is to measure website speed, both first-load and browsing speed.
Website speed has changed
Two new web development technologies have changed the game for site speed. The first is the rise of mature JavaScript application frameworks like React, Vue, and Angular. These frameworks make it easier to deliver websites as single-page applications, also known as progressive web apps, which don’t have to reload the whole page after a click — think Gmail and Twitter on your mobile browser.
The second is widespread support on both Android phones and iPhones for new features that enable PWAs, which are websites that act like native apps, including instant page transitions, offline browsing, and push notifications. Above all, PWA features give developers greater control over browser caching and content prefetching, which are key to enabling
