Glossary · SEO & Search
WebPageTest
Overview
What WebPageTest is
WebPageTest is a detailed web performance testing tool, originally open-source and now maintained by Catchpoint. You enter a URL and choose a real test location, browser, device, and connection speed; it then loads the page on actual hardware and records precisely what happened. It's the go-to tool when PageSpeed Insights tells you a page is slow but not why.
What its reports show
WebPageTest produces a request-by-request waterfall chart, so you can see every file the page loads, in what order, and how long each takes. It captures Core Web Vitals, a visual filmstrip and video of the load, first- and repeat-view timings, and an optimization checklist. Advanced options include multi-step scripting, side-by-side A/B comparisons of two URLs, and testing from dozens of global locations.
How we use it in technical SEO
For SEO and technical SEO work, WebPageTest is our deep-diagnostics tool. When a client's Core Web Vitals fail, its waterfall pinpoints the render-blocking scripts, slow third-party tags, or unoptimized images causing the delay, so developers fix the true bottleneck rather than guessing. Testing from a specific location and throttled connection also shows how the site performs for real users, not just on fast office networks.
Where we use it
Related Zen in Tech services
How our team puts WebPageTest to work in real projects.
FAQ
WebPageTest — common questions
WebPageTest vs PageSpeed Insights?
PageSpeed Insights gives a quick score and high-level fixes; WebPageTest offers far deeper diagnostics, including request-level waterfalls, filmstrips, custom locations, and scripting. Many teams start with PageSpeed Insights and switch to WebPageTest to investigate root causes.
Is WebPageTest free?
Yes. WebPageTest offers a free public version for on-demand tests. Catchpoint also sells paid plans with higher test volumes, private instances, API access, and continuous monitoring for teams that need them.
What is a waterfall chart in WebPageTest?
A waterfall chart lists every network request a page makes as a stacked timeline, showing when each file starts and finishes loading. It reveals bottlenecks like slow servers, large assets, and render-blocking resources.
Keep exploring
Related terms
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