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






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


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


Google Analytics, mPulse, Glimpse, etc.

Real user monitoring

Median load time for various audience demographics


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 ...

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