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https://whatwg.org

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
98
GRADE
A+
FIX
1
REVIEW
2
PASS
12
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
100
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
97
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

807 ms

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

807 ms

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

0 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.000

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

1.33 s

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

807 ms

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
17
12 PASS 2 REVIEW 1 FIX
D
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

B
Image Optimization
6 images, 0 KB saveable
REVIEW
6 images, 0 KB saveable
Info::
All images are well-optimized
6 images 4 KB
0 oversized -0 KB
6 legacy format
0 missing dimensions CLS risk
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
7 KB transferred, 9 requests
PASS
7 KB transferred, 9 requests
Info::
Page weighs 12 KB (7 KB transferred)
Info::
9 HTTP requests
Info::
Estimated 0.00 g CO2 per page load
7 KB / 2.4 MB budget
7 KB transferred
9 requests
0.00 g CO2 per page load
Images 4.4 KiB 59%
HTML 1.9 KiB 26%
CSS 1.1 KiB 15%
Other 0 B 0%
0 2.4 MB 4.9 MB
Under budget
A+
Third-Party Impact
7% third-party, 0 ms blocking
PASS
7% third-party, 0 ms blocking
Info::
Third-party code accounts for 7% of page weight (507 B of 7.5 KiB)
Info::
Third-party blocking time is low (0 ms)
93%
First-party Third-party
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
JS Execution Cost
367ms total JS execution
PASS
367ms total JS execution
Info::
Unattributable: 240ms CPU time
Info::
https://whatwg.org/: 127ms CPU time
Warning::
Third-party scripts: 240ms (65% of total)

Main Thread Breakdown

Other 63% Style & Layout 23% Script Evaluation 6% Rendering 5%
ScriptTotalScriptingParse/CompileParty
Unattributable240ms10ms0ms3rd
https://whatwg.org/127ms8ms2ms1st
A+
Font Loading
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
A+
JS Bundles
No JavaScript
PASS
No JavaScript
Info::
No JavaScript bundles
No JavaScript files loaded.
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A+
Page Weight Inventory
9 resources · 7 KB · 0 KB savings available
PASS
9 resources · 7 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 7 KB
Info::
2 third-party resources (7% of weight)
9 resources · 7.5 KiB · 2 third-party Within 1MB page-weight target
Image 59% · 4.4 KiB
Document 26% · 1.9 KiB
CSS 15% · 1.1 KiB
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
Network Waterfall
9 requests over 922ms
INFO
0 ms 200 ms 400 ms 600 ms 800 ms FCP 807 ms LCP 807 mshttps://whatwg.org// https://whatwg.org/ — 200 — 1.9 KiB — 546 ms — h2https://whatwg.org/style/shared.css/style/shared.css https://whatwg.org/style/shared.css — 200 — 1.1 KiB — 80 ms — h2https://resources.whatwg.org/logo.svgresources.whatwg.org/logo.svg https://resources.whatwg.org/logo.svg — 200 — 507 B — 343 ms — h2https://whatwg.org/img/arrow.svg/img/arrow.svg https://whatwg.org/img/arrow.svg — 200 — 600 B — 81 ms — h2https://whatwg.org/img/participate.svg/img/participate.svg https://whatwg.org/img/participate.svg — 200 — 709 B — 83 ms — h2https://whatwg.org/img/chat.svg/img/chat.svg https://whatwg.org/img/chat.svg — 200 — 1.3 KiB — 86 ms — h2https://whatwg.org/img/x.svg/img/x.svg https://whatwg.org/img/x.svg — 200 — 520 B — 87 ms — h2https://whatwg.org/img/checker.svg/img/checker.svg https://whatwg.org/img/checker.svg — 200 — 813 B — 89 ms — h2https://resources.whatwg.org/logo.svgresources.whatwg.org/logo.svg https://resources.whatwg.org/logo.svg — 200 — 0 B — 3 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
65% of JavaScript execution is third-party
First-party Third-party 240ms · 0KB · $3/mo
Unattributable
Other
Costly
Execution 240ms
Transfer 0 KB
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • Unattributable adds 240ms and costs ~$3/month

65% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

Unattributable takes 240ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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