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Get Started Free →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.
.claude/skills/thedaviddias-webpagetest/SKILL.md| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-04 | ✓→✓ | ＝ Same ✓ | 5% | 0% |
| case-05 | ✓→✓ | ＝ Same ✓ | -28% | 0% |
| case-06 | ✓→✓ | ＝ Same ✓ | -18% | 0% |
| case-07 | ✓→✓ | ＝ Same ✓ | -42% | 0% |
| case-08 | ✓→✓ | ＝ Same ✓ | -5% | 0% |
WebPageTest reveals real-world performance issues that synthetic tools miss—like TTFB from actual locations, render-blocking patterns, and third-party script impact.
Use WebPageTest to analyze page performance, identify bottlenecks, and measure real-world loading metrics across different devices and connections.
Implement recommended optimizations from WebPageTest results including resource compression, caching, and critical path improvements.
Explain how WebPageTest provides insights into Core Web Vitals, loading waterfalls, and performance opportunities that synthetic testing can't reveal.
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.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/html/webpagetest
| Case | Status | Duration (ms) | Turns | Tokens | Tool calls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Without | With | Δ | Without | With | Δ | Without | With | Δ | Without | With | Δ | ||
case-01 | fail→fail | 7,372 | 10,402 | +41% | 1 | 1 | 0% | 1,191 | 2,065 | +73% | 0 | 0 | — |
case-02 | fail→fail | 15,357 | 11,291 | -26% | 1 | 1 | 0% | 2,840 | 2,405 | -15% | 0 | 0 | — |
case-03 | fail→fail | 18,916 | 15,010 | -21% | 1 | 1 | 0% | 3,080 | 2,510 | -19% | 0 | 0 | — |
case-04 | pass→pass | 11,489 | 9,646 | -16% | 1 | 1 | 0% | 2,079 | 2,191 | +5% | 0 | 0 | — |
case-05 | pass→pass | 7,462 | 4,417 | -41% | 1 | 1 | 0% | 1,504 | 1,088 | -28% | 0 | 0 | — |
case-06 | pass→pass | 14,657 | 10,546 | -28% | 1 | 1 | 0% | 2,684 | 2,206 | -18% | 0 | 0 | — |
case-07 | pass→pass | 12,896 | 5,457 | -58% | 1 | 1 | 0% | 1,976 | 1,140 | -42% | 0 | 0 | — |
case-08 | pass→pass | 11,173 | 8,790 | -21% | 1 | 1 | 0% | 1,723 | 1,642 | -5% | 0 | 0 | — |
case-09 | pass→pass | 8,827 | 5,297 | -40% | 1 | 1 | 0% | 1,487 | 1,192 | -20% | 0 | 0 | — |
case-10 | pass→pass | 10,625 | 6,341 | -40% | 1 | 1 | 0% | 1,904 | 1,287 | -32% | 0 | 0 | — |
case-11 | pass→pass | 11,414 | 10,611 | -7% | 1 | 1 | 0% | 1,852 | 1,898 | +2% | 0 | 0 | — |
case-12 | pass→pass | 10,545 | 6,660 | -37% | 1 | 1 | 0% | 1,711 | 1,503 | -12% | 0 | 0 | — |
case-13 | pass→pass | 8,876 | 5,531 | -38% | 1 | 1 | 0% | 1,625 | 1,284 | -21% | 0 | 0 | — |
case-14 | pass→pass | 17,012 | 13,916 | -18% | 1 | 1 | 0% | 2,730 | 2,518 | -8% | 0 | 0 | — |
case-15 | pass→pass | 9,798 | 6,545 | -33% | 1 | 1 | 0% | 1,706 | 1,434 | -16% | 0 | 0 | — |
case-16 | pass→pass | 10,834 | 7,640 | -29% | 1 | 1 | 0% | 2,016 | 1,632 | -19% | 0 | 0 | — |
case-17 | pass→pass | 15,156 | 12,901 | -15% | 1 | 1 | 0% | 2,520 | 2,271 | -10% | 0 | 0 | — |
case-18 | pass→pass | 13,832 | 10,954 | -21% | 1 | 1 | 0% | 2,529 | 2,392 | -5% | 0 | 0 | — |
case-19 | pass→pass | 11,150 | 6,538 | -41% | 1 | 1 | 0% | 2,135 | 1,366 | -36% | 0 | 0 | — |
case-20 | pass→pass | 15,303 | 10,220 | -33% | 1 | 1 | 0% | 2,451 | 1,703 | -31% | 0 | 0 | — |
case-21 | pass→pass | 6,989 | 5,384 | -23% | 1 | 1 | 0% | 1,241 | 1,164 | -6% | 0 | 0 | — |
case-22 | pass→pass | 14,966 | 11,071 | -26% | 1 | 1 | 0% | 2,539 | 2,218 | -13% | 0 | 0 | — |
DecimalAI ran this skill against gemini-3.6-flash twice over the same eval suite — once with the skill loaded and once without — and compared the two runs case by case. 22 cases were attempted. The headline lift of 0 percentage points is the difference between those two pass rates over the 22 comparable cases.
Other measured skills in the registry, with their headline benchmark lift.