Skip to content
https://js.org

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
96
GRADE
A
FIX
0
REVIEW
1
PASS
12
INFO
1

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.
93
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
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.

457 ms

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

457 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.

0.002

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

457 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.

457 ms

Page Load Progression

458 ms
915 ms
1.4 s
1.8 s
2.3 s
2.7 s
3.2 s
3.7 s
Checks
14
12 PASS 1 REVIEW
B
Third-Party Impact
45% third-party, 0 ms blocking
REVIEW
45% third-party, 0 ms blocking
Info::
Third-party code accounts for 45% of page weight (31.8 KiB of 70.7 KiB)
Info::
Third-party blocking time is low (0 ms)
55%
45%
First-party Third-party
A+
Page Weight Budget
71 KB transferred, 16 requests
PASS
71 KB transferred, 16 requests
Info::
Page weighs 128 KB (71 KB transferred)
Info::
16 HTTP requests
Info::
Estimated 0.01 g CO2 per page load
71 KB / 2.4 MB budget
71 KB transferred
16 requests
0.01 g CO2 per page load
Fonts 30.1 KiB 43%
JavaScript 21.2 KiB 30%
Images 9.9 KiB 14%
HTML 6.3 KiB 9%
Other 1.9 KiB 3%
Other 787 B 1%
Other 667 B 1%
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+
Image Optimization
1 images, 0 KB saveable
PASS
1 images, 0 KB saveable
Info::
All images are well-optimized
1 images 10 KB
0 oversized -0 KB
1 legacy format
0 missing dimensions CLS risk
A+
JS Execution Cost
No JS execution data
PASS
No JS execution data
Info::
No significant JS execution detected

Main Thread Breakdown

Style & Layout 37% Other 35% Script Evaluation 18% Rendering 5%
A+
Font Loading
2 fonts (30 KB)
PASS
2 fonts (30 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

30 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 457 ms LCP 457 mshttps://js.org/fnt/source-sans-3-v9-latin-regular.woff2source-sans-3-v9-latin-... https://js.org/fnt/source-sans-3-v9-latin-regular.woff2 — 15.0 KiB — 28 ms — font-display: swaphttps://js.org/fnt/source-sans-3-v9-latin-600.woff2source-sans-3-v9-latin-... https://js.org/fnt/source-sans-3-v9-latin-600.woff2 — 15.0 KiB — 29 ms — font-display: swap
source-sans-3-v9-latin-... woff2 swap
Size 15 KB
Load time 28 ms
Start 267 ms
Risk FOUT — text flashes from fallback to web font
source-sans-3-v9-latin-... woff2 swap
Size 15 KB
Load time 29 ms
Start 268 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
4 scripts, 0 KB unused
PASS
4 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://js.org/main.js1 KB—✓1st
https://m.servedby-buysellads.com/monetization.custom.js7 KB—✓3rd
https://cdn.carbonads.com/carbon.js?serve=CESD4K3E&placement=jsorg10 KB—✓3rd
https://api.github.com/repos/js-org/js.org?callback=cb_xycscy5flf3 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
16 resources · 71 KB · 0 KB savings available
PASS
16 resources · 71 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 71 KB
Warning::
10 third-party resources (45% of weight)
16 resources · 70.7 KiB · 10 third-party Within 1MB page-weight target
Font 43% · 30.1 KiB
JavaScript 30% · 21.2 KiB
Image 15% · 10.6 KiB
Document 9% · 6.3 KiB
Other 4% · 2.5 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

A+
HTTP Caching
max-age=600 (10 minutes)
PASS
max-age=600 (10 minutes)
Info::
Cache-Control header is set
Got: max-age=600
Info::
Effective TTL: 10 minutes (max-age=600)
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

max-age=600

DirectiveValueMeaning
max-age600Cache for 10 minutes
Effective TTL: 600 seconds
Network Waterfall
16 requests over 1520ms
INFO
0 ms 500 ms 1.0 s 1.5 s FCP 457 ms LCP 457 mshttps://js.org// https://js.org/ — 200 — 6.3 KiB — 260 ms — h2https://js.org/fnt/source-sans-3-v9-latin-regular.woff2/fnt/source-sans-3-v9-latin-regular... https://js.org/fnt/source-sans-3-v9-latin-regular.woff2 — 200 — 15.0 KiB — 28 ms — h2https://js.org/fnt/source-sans-3-v9-latin-600.woff2/fnt/source-sans-3-v9-latin-600.wof... https://js.org/fnt/source-sans-3-v9-latin-600.woff2 — 200 — 15.0 KiB — 29 ms — h2https://js.org/main.js/main.js https://js.org/main.js — 200 — 1.1 KiB — 28 ms — h2https://m.servedby-buysellads.com/monetization.custom.jsm.servedby-buysellads.com/monetizat... https://m.servedby-buysellads.com/monetization.custom.js — 200 — 7.1 KiB — 11 ms — h2https://cdn.carbonads.com/carbon.js?serve=CESD4K3E&placement=jsorgcdn.carbonads.com/carbon.js?serve=C... https://cdn.carbonads.com/carbon.js?serve=CESD4K3E&placement=jsorg — 200 — 10.1 KiB — 11 ms — h2https://js.org/manifest.webmanifest/manifest.webmanifest https://js.org/manifest.webmanifest — 200 — 667 B — 168 ms — h2https://api.github.com/repos/js-org/js.org?callback=cb_xycscy5flfapi.github.com/repos/js-org/js.org?... https://api.github.com/repos/js-org/js.org?callback=cb_xycscy5flf — 200 — 2.9 KiB — 271 ms — h2https://srv.buysellads.com/ads/CWYDC23J.json?segment=placement:jsorg-badge-banner&v=truesrv.buysellads.com/ads/CWYDC23J.jso... https://srv.buysellads.com/ads/CWYDC23J.json?segment=placement:jsorg-badge-banner&v=true — 200 — 0 B — 85 ms — h2https://srv.carbonads.net/ads/CESD4K3E.json?segment=placement:jsorg&v=truesrv.carbonads.net/ads/CESD4K3E.json... https://srv.carbonads.net/ads/CESD4K3E.json?segment=placement:jsorg&v=true — 200 — 0 B — 104 ms — h2https://srv.buysellads.com/ads/CWYDC23J.json?segment=placement:jsorg-badge-banner&v=truesrv.buysellads.com/ads/CWYDC23J.jso... https://srv.buysellads.com/ads/CWYDC23J.json?segment=placement:jsorg-badge-banner&v=true — 200 — 981 B — 29 ms — h2https://srv.carbonads.net/ads/CESD4K3E.json?segment=placement:jsorg&v=truesrv.carbonads.net/ads/CESD4K3E.json... https://srv.carbonads.net/ads/CESD4K3E.json?segment=placement:jsorg&v=true — 200 — 782 B — 37 ms — h2https://srv.carbonads.net/static/30242/00d4b760afe6225b859ac1b17c21be5a03b282e4srv.carbonads.net/static/30242/00d4... https://srv.carbonads.net/static/30242/00d4b760afe6225b859ac1b17c21be5a03b282e4 — 200 — 9.9 KiB — 95 ms — h2https://xad.js.org/xad_cxad.js.org/xad_c https://xad.js.org/xad_c — -1 — 0 B — 54 ms — https://js.org/ico/favicon.svg/ico/favicon.svg https://js.org/ico/favicon.svg — 200 — 787 B — 38 ms — h2https://srv.carbonads.net/ads/viewable/x/GTND427UCYSI5KQ7CVB4YKQUCASI6KJUCEYDTZ3JCASI5K37C6BDE53KF6AIP23YCWYILKJYCABI527WCESD6KQKC6SI52JYCTYIKK3EHJSCL7ZUKHJCY7V?segment=placement:jsorgsrv.carbonads.net/ads/viewable/x/GT... https://srv.carbonads.net/ads/viewable/x/GTND427UCYSI5KQ7CVB4YKQUCASI6KJUCEYDTZ3JCASI5K37C6BDE53KF6AIP23YCWYILKJYCABI527WCESD6KQKC6SI52JYCTYIKK3EHJSCL7ZUKHJCY7V?segment=placement:jsorg — 200 — 150 B — 36 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

Send Feedback