Designing for Performance

Chapter 6. Measuring and Iterating on Performance

Benchmarks are not just critical to understanding the state of your user experience today, but they will also help you pinpoint what contributes to performance changes over time. Routine checks on various page speed metrics like total page load time, total page weight, and Speed Index for perceived performance for your major pages will enable you to see if things get slower on your site (and hopefully, why). Table 6-1 outlines the major tools you can use for benchmarking your site’s performance, many of which we’ll cover in this chapter.

Table 6-1. Benchmarking overview

Tool	Type	Benchmark	Timing
YSlow	Browser plug-in	Overall grade, recommendations	As you develop, then once every quarter
Chrome DevTools	Browser plug-in	Recommendations, waterfall chart, frames per second	As you develop, then once every quarter
WebPagetest	Sythentic testing	Overall grade, recommendations, waterfall chart, Speed Index	Every time you make a large change or experiment
Catchpoint, Gomez, wpt-script, etc.	Sythentic testing (trending)	Trends in your site’s performance over time	Monthly
Google Analytics, mPulse, Glimpse, etc.	Real user monitoring	Median load time for various audience demographics	Weekly

As sites age and change, there are plenty of opportunities for both improvements and degradations in performance; it’s imperative to keep an eye on these metrics using browser plug-ins, synthetic tests, and real user monitoring.

Browser Tools

To begin to see how well your site performs ...