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Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
89
GRADE
B
FIX
2
REVIEW
2
PASS
11
INFO
2

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

Mobile Desktop
96
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
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.
100
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.

2.05 s

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

2.50 s

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

4 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.

2.05 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.

2.54 s

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
11 PASS 2 REVIEW 2 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (656.4 KiB of 656.7 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
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.

No Cache-Control header

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

C
Image Optimization
Action
15 images, 0 KB saveable
REVIEW
15 images, 0 KB saveable
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/cms-uploads/_920xAUTO_crop_cent... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/cms-uploads/_920xAUTO_crop_cent... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/assets/logos/w3c-2025/svg/w3c.s... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/cms-uploads/_920xAUTO_crop_cent... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.w3.org/thumbnails/250/logos/organizati... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
15 images 485 KB
0 oversized -0 KB
12 legacy format
10 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

B
JS Execution Cost
734ms total JS execution
REVIEW
734ms total JS execution
Warning::
https://www.w3.org/: 429ms CPU time
Info::
Unattributable: 242ms CPU time
Info::
https://www.w3.org/assets/website-2021/js/main.js?...: 62ms CPU time
Warning::
Third-party scripts: 734ms (100% of total)

Main Thread Breakdown

Other 37% Style & Layout 35% Script Evaluation 12% Rendering 10% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
https://www.w3.org/429ms23ms5ms3rd
Unattributable242ms13ms0ms3rd
https://www.w3.org/assets/website-2021/js/main.js?ver=1.462ms47ms8ms3rd
A+
Page Weight Budget
657 KB transferred, 31 requests
PASS
657 KB transferred, 31 requests
Info::
Page weighs 822 KB (657 KB transferred)
Info::
31 HTTP requests
Info::
Estimated 0.13 g CO2 per page load
657 KB / 2.4 MB budget
657 KB transferred
31 requests
0.13 g CO2 per page load
Images 484.6 KiB 74%
CSS 55.0 KiB 8%
Other 48.5 KiB 7%
Fonts 34.3 KiB 5%
JavaScript 21.9 KiB 3%
HTML 9.9 KiB 2%
Other 2.3 KiB 0%
Other 343 B 0%
0 2.4 MB 4.9 MB
Under budget
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+
Font Loading
2 fonts (34 KB)
PASS
2 fonts (34 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

34 KB total

Render-blocking

0

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s 2.0 s 2.5 s FCP 2.0 s LCP 2.5 shttps://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2notosans-regular.woff2 https://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2 — 17.2 KiB — 48 ms — font-display: swaphttps://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2notosans-bold.woff2 https://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2 — 17.1 KiB — 37 ms — font-display: swap
notosans-regular.woff2 woff2 swap
Size 17 KB
Load time 48 ms
Start 173 ms
Risk FOUT — text flashes from fallback to web font
notosans-bold.woff2 woff2 swap
Size 17 KB
Load time 37 ms
Start 259 ms
Risk FOUT — text flashes from fallback to web font
Optimization checklist
  • Preload critical fonts (priority=high)
  • Use woff2 format for all fonts
  • Set font-display to swap, optional, or fallback
  • Subset large fonts (≤100 KB each)
A
JS Bundles
3 scripts, 0 KB unused
PASS
3 scripts, 0 KB unused
Warning::
https://www.w3.org/assets/website-2021/js/main.js?...: unminified — 6 KB could be saved
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.w3.org/assets/website-2021/js/libraries/fontfaceobserver.js3 KB—✓3rd
https://www.w3.org/assets/website-2021/js/main.js?ver=1.417 KB—✗3rd
https://www.w3.org/assets/website-2021/js/members.js1 KB—✓3rd
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
31 resources · 657 KB · 0 KB savings available
PASS
31 resources · 657 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 657 KB
Warning::
30 third-party resources (100% of weight)
31 resources · 656.7 KiB · 30 third-party Within 1MB page-weight target
Image 74% · 486.5 KiB
CSS 8% · 55.0 KiB
Media 7% · 48.5 KiB
Font 5% · 34.3 KiB
JavaScript 3% · 21.9 KiB
Document 2% · 9.9 KiB
Other 0% · 723 B
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
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall
31 requests over 449ms
INFO
0 ms 500 ms 1.0 s 1.5 s 2.0 s 2.5 s FCP 2.0 s LCP 2.5 shttps://w3.org// https://w3.org/ — 301 — 380 B — 67 ms — h2https://www.w3.org/www.w3.org/ https://www.w3.org/ — 200 — 9.9 KiB — 34 ms — h2https://www.w3.org/assets/website-2021/styles/core.css?ver=1.5www.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/core.css?ver=1.5 — 200 — 39.0 KiB — 47 ms — h2https://www.w3.org/assets/website-2021/styles/advanced.css?ver=1.5www.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/advanced.css?ver=1.5 — 200 — 10.0 KiB — 32 ms — h2https://www.w3.org/assets/website-2021/js/libraries/fontfaceobserver.jswww.w3.org/assets/website-2021/js/l... https://www.w3.org/assets/website-2021/js/libraries/fontfaceobserver.js — 200 — 3.1 KiB — 48 ms — h2https://www.w3.org/assets/logos/w3c-2025/svg/w3c.svgwww.w3.org/assets/logos/w3c-2025/sv... https://www.w3.org/assets/logos/w3c-2025/svg/w3c.svg — 200 — 31.0 KiB — 30 ms — h2https://www.w3.org/assets/website-2021/svg/search.svgwww.w3.org/assets/website-2021/svg/... https://www.w3.org/assets/website-2021/svg/search.svg — 200 — 984 B — 36 ms — h3https://www.w3.org/assets/website-2021/svg/avatar.svgwww.w3.org/assets/website-2021/svg/... https://www.w3.org/assets/website-2021/svg/avatar.svg — 200 — 1.0 KiB — 33 ms — h3https://www.w3.org/assets/website-2021/js/main.js?ver=1.4www.w3.org/assets/website-2021/js/m... https://www.w3.org/assets/website-2021/js/main.js?ver=1.4 — 200 — 17.5 KiB — 66 ms — h3https://www.w3.org/assets/website-2021/styles/print.csswww.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/print.css — 200 — 6.0 KiB — 36 ms — h3https://www.w3.org/assets/website-2021/js/members.jswww.w3.org/assets/website-2021/js/m... https://www.w3.org/assets/website-2021/js/members.js — 200 — 1.3 KiB — 31 ms — h3https://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2www.w3.org/assets/website-2021/font... https://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2 — 200 — 17.2 KiB — 48 ms — h3https://www.w3.org/cms-uploads/animation.mp4www.w3.org/cms-uploads/animation.mp... https://www.w3.org/cms-uploads/animation.mp4 — 206 — 48.5 KiB — 154 ms — h3data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPHN2ZyB2ZXJzaW9uPSIxL…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPHN2ZyB2ZXJzaW9uPSIxL… — 200 — 0 B — 0 ms — datahttps://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2www.w3.org/assets/website-2021/font... https://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2 — 200 — 17.1 KiB — 37 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/w30c-pattern.jpegwww.w3.org/cms-uploads/_920xAUTO_cr... https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/w30c-pattern.jpeg — 200 — 170.6 KiB — 179 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/ryan-quintal-US9Tc9pKNBU-unsplash.jpgwww.w3.org/cms-uploads/_920xAUTO_cr... https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/ryan-quintal-US9Tc9pKNBU-unsplash.jpg — 200 — 108.1 KiB — 172 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/marvin-meyer-SYTO3xs06fU-unsplash.jpgwww.w3.org/cms-uploads/_920xAUTO_cr... https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/marvin-meyer-SYTO3xs06fU-unsplash.jpg — 200 — 98.4 KiB — 171 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/86485.png?x-version=3www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/86485.png?x-version=3 — 200 — 18.6 KiB — 57 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/33823.png?x-version=3www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/33823.png?x-version=3 — 200 — 12.6 KiB — 153 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/28169.png?x-version=4www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/28169.png?x-version=4 — 200 — 3.5 KiB — 43 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/160564.png?x-version=1www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/160564.png?x-version=1 — 200 — 11.2 KiB — 47 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/127220.png?x-version=1www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/127220.png?x-version=1 — 200 — 17.4 KiB — 163 ms — h3https://www.w3.org/thumbnails/250/logos/organizations/10894.png?x-version=3www.w3.org/thumbnails/250/logos/org... https://www.w3.org/thumbnails/250/logos/organizations/10894.png?x-version=3 — 200 — 11.1 KiB — 152 ms — h3data:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd…data:image/svg+xml;base64,PHN2ZyBma... data:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd…data:image/svg+xml;base64,PHN2ZyBma... data:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd…data:image/svg+xml;base64,PHN2ZyBma... data:image/svg+xml;base64,PHN2ZyBmaWxsPSJXaW5kb3ciIGhlaWdodD0iMjQiIHZpZXdCb3g9IjAgMCAyNCAyNCIgd2lkd… — 200 — 0 B — 0 ms — datahttps://www.w3.org/account/user-menu/www.w3.org/account/user-menu/ https://www.w3.org/account/user-menu/ — 200 — 343 B — 138 ms — h3
0 ms 500 ms 1.0 s 1.5 s 2.0 s 2.5 s FCP 2.0 s LCP 2.5 shttps://w3.org// https://w3.org/ — 301 — 380 B — 67 ms — h2https://www.w3.org/www.w3.org/ https://www.w3.org/ — 200 — 9.9 KiB — 34 ms — h2https://www.w3.org/assets/website-2021/styles/core.css?ver=1.5www.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/core.css?ver=1.5 — 200 — 39.0 KiB — 47 ms — h2https://www.w3.org/assets/website-2021/styles/advanced.css?ver=1.5www.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/advanced.css?ver=1.5 — 200 — 10.0 KiB — 32 ms — h2https://www.w3.org/assets/website-2021/js/libraries/fontfaceobserver.jswww.w3.org/assets/website-2021/js/l... https://www.w3.org/assets/website-2021/js/libraries/fontfaceobserver.js — 200 — 3.1 KiB — 48 ms — h2https://www.w3.org/assets/logos/w3c-2025/svg/w3c.svgwww.w3.org/assets/logos/w3c-2025/sv... https://www.w3.org/assets/logos/w3c-2025/svg/w3c.svg — 200 — 31.0 KiB — 30 ms — h2https://www.w3.org/assets/website-2021/svg/search.svgwww.w3.org/assets/website-2021/svg/... https://www.w3.org/assets/website-2021/svg/search.svg — 200 — 984 B — 36 ms — h3https://www.w3.org/assets/website-2021/svg/avatar.svgwww.w3.org/assets/website-2021/svg/... https://www.w3.org/assets/website-2021/svg/avatar.svg — 200 — 1.0 KiB — 33 ms — h3https://www.w3.org/assets/website-2021/js/main.js?ver=1.4www.w3.org/assets/website-2021/js/m... https://www.w3.org/assets/website-2021/js/main.js?ver=1.4 — 200 — 17.5 KiB — 66 ms — h3https://www.w3.org/assets/website-2021/styles/print.csswww.w3.org/assets/website-2021/styl... https://www.w3.org/assets/website-2021/styles/print.css — 200 — 6.0 KiB — 36 ms — h3https://www.w3.org/assets/website-2021/js/members.jswww.w3.org/assets/website-2021/js/m... https://www.w3.org/assets/website-2021/js/members.js — 200 — 1.3 KiB — 31 ms — h3https://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2www.w3.org/assets/website-2021/font... https://www.w3.org/assets/website-2021/fonts/notosans/notosans-regular.woff2 — 200 — 17.2 KiB — 48 ms — h3https://www.w3.org/cms-uploads/animation.mp4www.w3.org/cms-uploads/animation.mp... https://www.w3.org/cms-uploads/animation.mp4 — 206 — 48.5 KiB — 154 ms — h3data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPCEtLSBHZW5lcmF0b3I6I… — 200 — 0 B — 0 ms — datadata:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPHN2ZyB2ZXJzaW9uPSIxL…data:image/svg+xml;base64,PD94bWwgd... data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0idXRmLTgiPz4KPHN2ZyB2ZXJzaW9uPSIxL… — 200 — 0 B — 0 ms — datahttps://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2www.w3.org/assets/website-2021/font... https://www.w3.org/assets/website-2021/fonts/notosans/notosans-bold.woff2 — 200 — 17.1 KiB — 37 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/w30c-pattern.jpegwww.w3.org/cms-uploads/_920xAUTO_cr... https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/w30c-pattern.jpeg — 200 — 170.6 KiB — 179 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/ryan-quintal-US9Tc9pKNBU-unsplash.jpgwww.w3.org/cms-uploads/_920xAUTO_cr... https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/ryan-quintal-US9Tc9pKNBU-unsplash.jpg — 200 — 108.1 KiB — 172 ms — h3https://www.w3.org/cms-uploads/_920xAUTO_crop_center-center_none/marvin-meyer-SYTO3xs06fU-unsplash.jpgwww.w3.org/cms-uploads/_920xAUTO_cr... 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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 734ms · 27KB · €8/mo
www.w3.org
Other
Costly
Execution 429ms
Transfer 10 KB
Monthly Cost €5/mo
Unattributable
Other
Costly
Execution 242ms
Transfer 0 KB
Monthly Cost €3/mo
www.w3.org
Other
Optional
Execution 62ms
Transfer 17 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • www.w3.org adds 429ms and costs ~€5/month
  • Unattributable adds 242ms and costs ~€3/month

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

www.w3.org takes 429ms 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

Unattributable takes 242ms 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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