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https://whatwg.org

Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
98
GRADE
A+
FIX
1
REVIEW
2
PASS
10
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.

516 ms

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

516 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.

557 ms

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

516 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
15
10 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
57ms total JS execution
PASS
57ms total JS execution
Info::
Unattributable: 57ms CPU time
Warning::
Third-party scripts: 57ms (100% of total)

Main Thread Breakdown

Other 58% Style & Layout 27% Script Evaluation 6% Rendering 5%
ScriptTotalScriptingParse/CompileParty
Unattributable57ms2ms0ms3rd
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
Network Waterfall
9 requests over 844ms
INFO
0 ms 200 ms 400 ms 600 ms 800 ms FCP 516 ms LCP 516 mshttps://whatwg.org// https://whatwg.org/ — 200 — 1.9 KiB — 332 ms — h2https://whatwg.org/style/shared.css/style/shared.css https://whatwg.org/style/shared.css — 200 — 1.1 KiB — 85 ms — h2https://resources.whatwg.org/logo.svgresources.whatwg.org/logo.svg https://resources.whatwg.org/logo.svg — 200 — 507 B — 478 ms — h2https://whatwg.org/img/arrow.svg/img/arrow.svg https://whatwg.org/img/arrow.svg — 200 — 600 B — 375 ms — h2https://whatwg.org/img/participate.svg/img/participate.svg https://whatwg.org/img/participate.svg — 200 — 709 B — 376 ms — h2https://whatwg.org/img/chat.svg/img/chat.svg https://whatwg.org/img/chat.svg — 200 — 1.3 KiB — 377 ms — h2https://whatwg.org/img/x.svg/img/x.svg https://whatwg.org/img/x.svg — 200 — 520 B — 379 ms — h2https://whatwg.org/img/checker.svg/img/checker.svg https://whatwg.org/img/checker.svg — 200 — 813 B — 381 ms — h2https://resources.whatwg.org/logo.svgresources.whatwg.org/logo.svg https://resources.whatwg.org/logo.svg — 200 — 0 B — 2 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 57ms · 0KB · $1/mo
Unattributable
Other
Optional
Execution 57ms
Transfer 0 KB
Monthly Cost $1/mo

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

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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