WebPageTest

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Introduction

WebPageTest is a web performance testing tool that loads pages in real browsers from locations around the world and produces detailed waterfalls, filmstrips, videos and Core Web Vitals metrics. It is owned by Catchpoint, which hosts the public service at webpagetest.org and maintains the open-source code at catchpoint/WebPageTest on GitHub.

WebPageTest is known for depth: request-level waterfalls, connection views, filmstrip comparisons, repeat-view testing, scripting of multi-step journeys, custom network throttling, and the ability to compare runs side by side. Catchpoint has added paid features, such as the WebPageTest API and experiments that let you test the impact of optimisations without deploying them.

The open-source repository shows lower activity than the hosted service: its latest GitHub release was 24.12 (December 2024) and the most recent push was in September 2025. When CheckOps checked, webpagetest.org served a human-verification challenge to automated requests, so pricing could not be confirmed.

In the quality loop WebPageTest belongs to the performance stage, used for deep investigation of slow pages and for before-and-after comparisons.

Features

1. Real browsers, many locations: Test from global locations and devices.
2. Waterfalls and filmstrips: Detailed request and visual progress analysis.
3. Scripting: Multi-step journeys and custom actions.
4. Comparisons: Side-by-side comparison of runs.
5. Core Web Vitals: LCP, CLS and other metrics per run.
6. API: Programmatic testing (paid via Catchpoint).

Pros

1. Depth of analysis: Among the most detailed free performance tools.
2. Real browsers: More realistic than simulated throttling.
3. Open-source code: Self-hosting is possible.

Cons

1. Open-source activity is low: Latest GitHub release December 2024.
2. Advanced features are paid: API and experiments require a plan.
3. Learning curve: Waterfalls take expertise to read.

Usage and Links (Example)

Open webpagetest.org, enter a URL, choose a location, browser and connection profile, and run with several repeats. Review the waterfall and filmstrip to find render-blocking resources and slow requests, then compare with a run after your fix.

Useful links:

• WebPageTest on GitHub

Pricing

Basic testing on webpagetest.org has historically been free with paid plans for the API and advanced features. See site; pricing could not be verified because the site blocked automated checks.

Recommended for?

• Performance engineers diagnosing slow pages
• Teams comparing optimisations before and after
• Developers who need real-browser tests from specific locations

Conclusion

WebPageTest remains one of the deepest tools for understanding how a page loads. Use it for diagnosis and comparisons, and combine it with monitoring tools for ongoing tracking.