Foreword
Considering the progress we’ve witnessed on the web in the last ten years, it’s surprising that we still struggle with slow websites today. In 2013, the world’s median mobile network connection was sub-3G. At such speeds, it was hard to deliver even reasonably-sized files quickly. Browsers could download only a handful of those files at once and had patchy support for crucial web features, making it hard to reduce the weight of the code we delivered. Further, the average mobile device had a fraction of the computing power of what we see today.
Fast Forward to today, network speeds are important but no longer our primary constraint. With widespread 3G, 4G, and expanding 5G coverage, network speed is less of an issue. Browsers are better too: they can download countless files at once, smartly select the resources appropriate for display, and render highly complex user interfaces out of consistent and minimal code. And while mobile device processing power still varies, baseline performance across devices has greatly improved.
With all this progress, our websites really should be faster. But it hasn’t turned out that way. As our technology improves, we develop increasingly complicated, shockingly heavier websites. And while fast networks may still deliver those sites’ files pretty quickly, some kinds of files–JavaScript, especially–can introduce lengthy delays after they’re delivered, particularly on the average mobile device. Worst of all, many sites rely on those already-heavy JavaScript files to subsequently fetch or generate their content, adding fragility and further delays to an already clunky stack.
In 2023, many performance problems are caused by the very patterns we’ve adopted. We’ve merely moved the performance burden from the network to the device.
But I’m here with good news: it doesn’t have to be this way. If our patterns are the problem, the solutions lie within our control. This guide provides a comprehensive view of modern performance concerns, explaining why performance matters, identifying and addressing performance bottlenecks, implementing continuous monitoring, and establishing a work culture that prioritizes performance.
There has never been a better time to deliver fast, resilient websites, but getting there demands an informed approach. So grab a hot beverage and let this guide illuminate the path forward. Rest assured; you’re in capable hands.
Scott Jehl
Author & Web Performance Advocate