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Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
88
GRADE
B
FIX
2
REVIEW
2
PASS
9
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.
77
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.

926 ms

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

1.24 s

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.

0.003

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

926 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.

1.24 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
15
9 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 (676.9 KiB of 677.3 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.

B
Image Optimization
8 images, 0 KB saveable
REVIEW
8 images, 0 KB saveable
Info::
All images are well-optimized
8 images 334 KB
0 oversized -0 KB
8 legacy format
0 missing dimensions CLS risk
B
JS Bundles
3 scripts, 52 KB unused
REVIEW
3 scripts, 52 KB unused
Warning::
https://www.ietf.org/static/dist/main.e2d621c55276...: 52 KB unused (78%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 52 KB
52 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.ietf.org/static/dist/main.e2d621c55276.js67 KB52 KB (78%)✓3rd
https://analytics.ietf.org/matomo.js22 KB—✓3rd
https://www.ietf.org/cdn-cgi/challenge-platform/h/g/scripts/jsd/b0a7532ac8ec/main.js?14 KB—✓3rd

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

A+
Page Weight Budget
677 KB transferred, 21 requests
PASS
677 KB transferred, 21 requests
Info::
Page weighs 1.3 MB (677 KB transferred)
Info::
21 HTTP requests
Info::
Estimated 0.14 g CO2 per page load
677 KB / 2.4 MB budget
677 KB transferred
21 requests
0.14 g CO2 per page load
Images 334.4 KiB 49%
Fonts 168.7 KiB 25%
JavaScript 103.6 KiB 15%
CSS 51.7 KiB 8%
HTML 9.1 KiB 1%
Other 8.5 KiB 1%
Other 1.2 KiB 0%
Other 0 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+
JS Execution Cost
229ms total JS execution
PASS
229ms total JS execution
Info::
https://www.ietf.org/: 92ms CPU time
Info::
https://www.ietf.org/cdn-cgi/challenge-platform/sc...: 77ms CPU time
Info::
Unattributable: 60ms CPU time
Warning::
Third-party scripts: 229ms (100% of total)

Main Thread Breakdown

Script Evaluation 43% Other 26% Style & Layout 21% Parse HTML & CSS 3% Script Parsing & Compilation 3%
ScriptTotalScriptingParse/CompileParty
https://www.ietf.org/92ms19ms1ms3rd
https://www.ietf.org/cdn-cgi/challenge-platform/scripts/jsd/main.js77ms72ms1ms3rd
Unattributable60ms3ms0ms3rd
A+
Font Loading
2 fonts (169 KB)
PASS
2 fonts (169 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

169 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 FCP 926 ms LCP 1.2 shttps://static.ietf.org/fonts/inter/inter-latin.woff2inter-latin.woff2 https://static.ietf.org/fonts/inter/inter-latin.woff2 — 37.5 KiB — 99 ms — font-display: swaphttps://www.ietf.org/static/dist/92ea18a81d737146ff044ddb52010366.84a4d15b9e44.woff292ea18a81d737146ff044dd... https://www.ietf.org/static/dist/92ea18a81d737146ff044ddb52010366.84a4d15b9e44.woff2 — 131.2 KiB — 40 ms — font-display: swap
inter-latin.woff2 woff2 swap
Size 38 KB
Load time 99 ms
Start 294 ms
Risk FOUT — text flashes from fallback to web font
92ea18a81d737146ff044dd... woff2 swap
Size 131 KB
Load time 40 ms
Start 295 ms
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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)

Fixing the unchecked items could save ~66 KB and ~132 ms

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
21 resources · 677 KB · 52 KB savings available
PASS
21 resources · 677 KB · 52 KB savings available
Info::
Within 1MB page-weight target
Got: 677 KB
Info::
~52 KB of savings available
Warning::
20 third-party resources (100% of weight)
21 resources · 677.3 KiB · 20 third-party Within 1MB page-weight target
Image 49% · 334.4 KiB
Font 25% · 168.7 KiB
JavaScript 15% · 103.6 KiB
CSS 8% · 51.7 KiB
Document 2% · 16.8 KiB
Other 0% · 2.0 KiB

~52.3 KiB of savings available

Remove unused JavaScript: 52.3 KiB
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
21 requests over 716ms
INFO
0 ms 500 ms 1.0 s FCP 926 ms LCP 1.2 shttps://ietf.org// https://ietf.org/ — 301 — 398 B — 44 ms — h3https://www.ietf.org/www.ietf.org/ https://www.ietf.org/ — 200 — 9.1 KiB — 72 ms — h3https://static.ietf.org/fonts/inter/import.cssstatic.ietf.org/fonts/inter/import.... https://static.ietf.org/fonts/inter/import.css — 200 — 867 B — 44 ms — h3https://www.ietf.org/static/dist/main.e2d621c55276.jswww.ietf.org/static/dist/main.e2d62... https://www.ietf.org/static/dist/main.e2d621c55276.js — 200 — 67.5 KiB — 121 ms — h3https://www.ietf.org/static/dist/main.0eac74df034a.csswww.ietf.org/static/dist/main.0eac7... https://www.ietf.org/static/dist/main.0eac74df034a.css — 200 — 50.9 KiB — 94 ms — h3https://static.ietf.org/logos/ietf.svgstatic.ietf.org/logos/ietf.svg https://static.ietf.org/logos/ietf.svg — 200 — 1.9 KiB — 45 ms — h3https://www.ietf.org/media/images/ietf-logo.width-600.jpgwww.ietf.org/media/images/ietf-logo... https://www.ietf.org/media/images/ietf-logo.width-600.jpg — 200 — 24.7 KiB — 110 ms — h3https://www.ietf.org/media/images/things.width-600.jpgwww.ietf.org/media/images/things.wi... https://www.ietf.org/media/images/things.width-600.jpg — 200 — 29.9 KiB — 95 ms — h3https://www.ietf.org/media/images/_MG_4832.width-600.jpgwww.ietf.org/media/images/_MG_4832.... https://www.ietf.org/media/images/_MG_4832.width-600.jpg — 200 — 48.1 KiB — 99 ms — h3https://www.ietf.org/media/images/IMG_15.width-600.jpgwww.ietf.org/media/images/IMG_15.wi... https://www.ietf.org/media/images/IMG_15.width-600.jpg — 200 — 40.9 KiB — 98 ms — h3https://www.ietf.org/media/images/vienna.height-245.jpgwww.ietf.org/media/images/vienna.he... https://www.ietf.org/media/images/vienna.height-245.jpg — 200 — 45.2 KiB — 108 ms — h3https://www.ietf.org/media/images/111-SanFrancisco.height-245.jpgwww.ietf.org/media/images/111-SanFr... https://www.ietf.org/media/images/111-SanFrancisco.height-245.jpg — 200 — 14.2 KiB — 101 ms — h3https://www.ietf.org/media/images/IETF125-banner.max-4000x4000.pngwww.ietf.org/media/images/IETF125-b... https://www.ietf.org/media/images/IETF125-banner.max-4000x4000.png — 200 — 129.5 KiB — 35 ms — h3https://static.ietf.org/fonts/inter/inter-latin.woff2static.ietf.org/fonts/inter/inter-l... https://static.ietf.org/fonts/inter/inter-latin.woff2 — 200 — 37.5 KiB — 99 ms — h2https://www.ietf.org/static/dist/92ea18a81d737146ff044ddb52010366.84a4d15b9e44.woff2www.ietf.org/static/dist/92ea18a81d... https://www.ietf.org/static/dist/92ea18a81d737146ff044ddb52010366.84a4d15b9e44.woff2 — 200 — 131.2 KiB — 40 ms — h3https://analytics.ietf.org/matomo.jsanalytics.ietf.org/matomo.js https://analytics.ietf.org/matomo.js — 200 — 22.4 KiB — 43 ms — h3https://www.ietf.org/cdn-cgi/challenge-platform/scripts/jsd/main.jswww.ietf.org/cdn-cgi/challenge-plat... https://www.ietf.org/cdn-cgi/challenge-platform/scripts/jsd/main.js — 302 — 450 B — 23 ms — h3https://analytics.ietf.org/matomo.php?action_name=IETF%20%7C%20Internet%20Engineering%20Task%20Force&idsite=1&rec=1&r=635166&h=17&m=35&s=18&url=https%3A%2F%2Fwww.ietf.org%2F&_id=&_idn=1&send_image=0&_refts=0&pv_id=DdXFqy&pf_net=31&pf_srv=39&pf_tfr=3&pf_dm1=201&uadata=%7B%22formFactors%22%3A%5B%22Desktop%22%5D%2C%22fullVersionList%22%3A%5B%7B%22brand%22%3A%22Chromium%22%2C%22version%22%3A%22147.0.7727.55%22%7D%2C%7B%22brand%22%3A%22Not.A%2FBrand%22%2C%22version%22%3A%228.0.0.0%22%7D%5D%2C%22mobile%22%3Afalse%2C%22model%22%3A%22%22%2C%22platform%22%3A%22macOS%22%2C%22platformVersion%22%3A%2210.15.7%22%7D&pdf=1&qt=0&realp=0&wma=0&fla=0&java=0&ag=0&cookie=1&res=800x600analytics.ietf.org/matomo.php?actio... https://analytics.ietf.org/matomo.php?action_name=IETF%20%7C%20Internet%20Engineering%20Task%20Force&idsite=1&rec=1&r=635166&h=17&m=35&s=18&url=https%3A%2F%2Fwww.ietf.org%2F&_id=&_idn=1&send_image=0&_refts=0&pv_id=DdXFqy&pf_net=31&pf_srv=39&pf_tfr=3&pf_dm1=201&uadata=%7B%22formFactors%22%3A%5B%22Desktop%22%5D%2C%22fullVersionList%22%3A%5B%7B%22brand%22%3A%22Chromium%22%2C%22version%22%3A%22147.0.7727.55%22%7D%2C%7B%22brand%22%3A%22Not.A%2FBrand%22%2C%22version%22%3A%228.0.0.0%22%7D%5D%2C%22mobile%22%3Afalse%2C%22model%22%3A%22%22%2C%22platform%22%3A%22macOS%22%2C%22platformVersion%22%3A%2210.15.7%22%7D&pdf=1&qt=0&realp=0&wma=0&fla=0&java=0&ag=0&cookie=1&res=800x600 — 204 — 0 B — 341 ms — h3https://www.ietf.org/cdn-cgi/challenge-platform/h/g/scripts/jsd/b0a7532ac8ec/main.js?www.ietf.org/cdn-cgi/challenge-plat... https://www.ietf.org/cdn-cgi/challenge-platform/h/g/scripts/jsd/b0a7532ac8ec/main.js? — 200 — 13.6 KiB — 26 ms — h3https://www.ietf.org/favicon.icowww.ietf.org/favicon.ico https://www.ietf.org/favicon.ico — 404 — 7.7 KiB — 36 ms — h3https://www.ietf.org/cdn-cgi/challenge-platform/h/g/jsd/oneshot/b0a7532ac8ec/0.5318469050084949:1776359656:ln3RLbZdcwVQxb75aXDKAHo1AsFFcq1l_zzfP5ot_C8/9ed4f21b2e11698cwww.ietf.org/cdn-cgi/challenge-plat... https://www.ietf.org/cdn-cgi/challenge-platform/h/g/jsd/oneshot/b0a7532ac8ec/0.5318469050084949:1776359656:ln3RLbZdcwVQxb75aXDKAHo1AsFFcq1l_zzfP5ot_C8/9ed4f21b2e11698c — 200 — 1.2 KiB — 26 ms — h3
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 229ms · 10KB · €2/mo
www.ietf.org
Other
Optional
Execution 92ms
Transfer 9 KB
Monthly Cost €1/mo
www.ietf.org
Other
Optional
Execution 77ms
Transfer 0 KB
Monthly Cost €1/mo
Unattributable
Other
Optional
Execution 60ms
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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