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name: webpagetest description: "Use when reviewing templates, rendered HTML, or shared components related to Analyze performance with WebPageTest. Validate the final browser-facing markup, not just the source framework abstraction." metadata: category: html priority: high difficulty: intermediate estimatedTime: "30" source: frontendchecklist.io url: https://frontendchecklist.io/rules/html/webpagetest

Analyze performance with WebPageTest

WebPageTest reveals real-world performance issues that synthetic tools miss—like TTFB from actual locations, render-blocking patterns, and third-party script impact.

Quick Reference

• Run 3+ tests to get consistent results
• Test from locations near your users
• Use filmstrip view to identify visual progress
• Check waterfall for blocking resources and slow third-parties

Check

Use WebPageTest to analyze page performance, identify bottlenecks, and measure real-world loading metrics across different devices and connections.

Fix

Implement recommended optimizations from WebPageTest results including resource compression, caching, and critical path improvements.

Explain

Explain how WebPageTest provides insights into Core Web Vitals, loading waterfalls, and performance opportunities that synthetic testing can't reveal.

Code Review

Review templates, server-rendered HTML, and shared components that output markup related to Analyze performance with WebPageTest. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/rules/html/webpagetest