Today I’ll show you how to analyze your web pages’ performance—whether in development, staging, or production—using tools from WebPageTest and Sitespeed.io.

Why Fast Web Pages Matter

It’s well-established that page load speed directly impacts user experience. Faster response and execution times are essential for all websites. Recent studies show that 57% of users will abandon a site if it takes more than 3 seconds to load. Among those users, 80% report they’ll never return after this poor first experience. Sites loading in 58+ seconds have bounce rates 2x higher than those loading in 1 second.

For e-commerce sites, the impact is even more pronounced. Studies indicate that each additional second of load time reduces conversion rates by an average of 7%. The same research found that 20% of cart abandonments are due to load times users perceive as “too long.”

Real-World Impact

Some compelling examples:

• Amazon: A 100ms (0.1 second) increase in load time equals a 1% loss in sales—which in 2016 would have represented €1.36 billion in lost revenue
• Shopzilla: Reducing load time from 7 to 2 seconds increased revenue by 7-12%
• Etam: Reported in 2015 that reducing average page load time by 0.7 seconds led to a 20% increase in conversion rate

SEO Implications

Google increasingly prioritizes page optimization for user experience, especially for mobile users. Ignoring your site’s load time is no longer an option for good SEO rankings.

Available Tools

To test web performance, you need the right tools. Today we’ll explore two excellent options: Sitespeed.io and WebPageTest.

Both tools are open-source and maintained by active communities to meet Google’s latest criteria for web performance and accessibility. I won’t detail their usage here—the documentation is comprehensive and well-explained.

Instead, we’ll address a common enterprise need: testing pages locally that aren’t accessible from outside a private network. I’ve created a repository that lets you test websites locally using WebPageTest or Sitespeed.io: WebPerformance.

Requirements

To run these scripts, you’ll need:

• Docker
• Node.js
• Firefox and/or Chrome

Installation for each is straightforward—just follow the official documentation.

Features

The scripts are simple but powerful, allowing you to:

• Test websites with bandwidth throttling for realistic conditions
• Test pages with mobile user agents (using Chrome)
• Run tests on pages not publicly accessible

Conclusion

These tools are fantastic for revealing both weaknesses and strengths in your websites. They enable teams to centralize improvement efforts around the same metrics Google uses. If there’s interest, I can follow up with an article exploring specific techniques to improve user experience on your websites.