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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
73
GRADE
C
FIX
4
REVIEW
3
PASS
5
INFO
2

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

Mobile Desktop
82
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.
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.

1.09 s

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

1.21 s

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

275 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.

1.62 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.

2.95 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
14
5 PASS 3 REVIEW 4 FIX
D
Page Weight Budget
Action
2.2 MB transferred, 54 requests
FIX
2.2 MB transferred, 54 requests
Info::
Page weighs 7.2 MB (2.2 MB transferred)
Warning::
JavaScript is 951 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 951 KB
Info::
54 HTTP requests
Info::
Estimated 0.46 g CO2 per page load
2.2 MB / 2.4 MB budget
2.2 MB transferred
54 requests
0.46 g CO2 per page load
JavaScript 951.2 KiB 43%
Images 905.4 KiB 41%
Other 159.4 KiB 7%
Fonts 112.2 KiB 5%
HTML 38.8 KiB 2%
CSS 28.9 KiB 1%
Other 26.0 KiB 1%
Other 0 B 0%
0 2.4 MB 4.9 MB
Approaching limit

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

D
Third-Party Impact
Action
97% third-party, 0 ms blocking
FIX
97% third-party, 0 ms blocking
Warning::
Third-party code accounts for 97% of page weight (2.1 MiB of 2.2 MiB)
Info::
Third-party blocking time is low (0 ms)
97%
First-party Third-party
D
JS Bundles
Action
16 scripts, 389 KB unused
FIX
16 scripts, 389 KB unused
Warning::
https://securepubads.g.doubleclick.net/pagead/mana...: 138 KB unused (76%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-NLX...: 76 KB unused (44%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-PVB...: 59 KB unused (50%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cdn.arstechnica.net/wp-content/themes/ars-...: 58 KB unused (82%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://ads-static.conde.digital/production/cns/bu...: 32 KB unused (80%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 389 KB
389 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202603310101/pubads_impl.js182 KB138 KB (76%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NLXNPCQ173 KB76 KB (44%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-PVBXQMCR&gtm=4e6411118 KB59 KB (50%)✓3rd
https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/js/app.25ba18.js71 KB58 KB (82%)✓3rd
https://ads-static.conde.digital/production/cns/builds/ars-technica/ars-technica.min.js41 KB32 KB (80%)✓3rd
https://cdn.arstechnica.net/wp/wp-includes/js/jquery/jquery.min.js?ver=3.7.134 KB24 KB (73%)✓3rd
https://arstechnica.com/wp-content/themes/ars-v9/public/js/cntracking.8e5b8b.js32 KB—✓1st
https://cdn.arstechnica.net/wp-content/plugins/article-forum-connect/public/js/iframe.js?ver=1.2.42 KB—✓3rd
https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/js/stats.74db3c.js4 KB—✓3rd
https://cdn.arstechnica.net/wp-content/plugins/article-forum-connect/public/js/iframe-resizer.parent.js?ver=5.3.18 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

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

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

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

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

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
21 images, 0 KB saveable
REVIEW
21 images, 0 KB saveable
Warning::
https://cdn.arstechnica.net/wp-content/uploads/202... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
21 images 905 KB
0 oversized -0 KB
21 legacy format
1 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

C
JS Execution Cost
Action
1362ms total JS execution
REVIEW
1362ms total JS execution
Warning::
https://arstechnica.com/: 328ms CPU time
Info::
https://privacy.condenastdigital.com/fides.js?prop...: 238ms CPU time
Info::
https://cdn.arstechnica.net/wp-content/themes/ars-...: 236ms CPU time
Info::
Unattributable: 206ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-NLX...: 146ms CPU time
Warning::
Third-party scripts: 1034ms (76% of total)

Main Thread Breakdown

Script Evaluation 50% Other 15% Style & Layout 14% Script Parsing & Compilation 12% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
https://arstechnica.com/328ms24ms5ms1st
https://privacy.condenastdigital.com/fides.js?property_id=FDS-MIKT8M&238ms133ms91ms3rd
https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/js/app.25ba18.js236ms182ms8ms3rd
Unattributable206ms6ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-NLXNPCQ146ms119ms25ms3rd
https://securepubads.g.doubleclick.net/pagead/managed/js/gpt/m202603310101/pubads_impl.js128ms103ms23ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-PVBXQMCR&gtm=4e641181ms64ms15ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

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
4 fonts (112 KB)
PASS
4 fonts (112 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

112 KB total

Render-blocking

0

of 4

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 1.1 s LCP 1.2 shttps://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/nwpStKy2OAdR1K-IwhWudF-R3w8aZQ.bf9a29.woff2nwpStKy2OAdR1K-IwhWudF-... https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/nwpStKy2OAdR1K-IwhWudF-R3w8aZQ.bf9a29.woff2 — 24.7 KiB — 0 ms — font-display: swaphttps://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/7cHmv4okm5zmbtYoK-4.a71c5e.woff27cHmv4okm5zmbtYoK-4.a71... https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/7cHmv4okm5zmbtYoK-4.a71c5e.woff2 — 39.2 KiB — 0 ms — font-display: swaphttps://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/XLYlIZPxYpJfTbZAFV-_Hcw.6df07f.woff2XLYlIZPxYpJfTbZAFV-_Hcw... https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/XLYlIZPxYpJfTbZAFV-_Hcw.6df07f.woff2 — 24.0 KiB — 0 ms — font-display: swaphttps://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/nwpMtKy2OAdR1K-IwhWudF-R3woqZ-LY.802cca.woff2nwpMtKy2OAdR1K-IwhWudF-... https://cdn.arstechnica.net/wp-content/themes/ars-v9/public/fonts/nwpMtKy2OAdR1K-IwhWudF-R3woqZ-LY.802cca.woff2 — 24.4 KiB — 0 ms — font-display: swap
nwpStKy2OAdR1K-IwhWudF-... woff2 swap
Size 25 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
7cHmv4okm5zmbtYoK-4.a71... woff2 swap
Size 39 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
XLYlIZPxYpJfTbZAFV-_Hcw... woff2 swap
Size 24 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
nwpMtKy2OAdR1K-IwhWudF-... woff2 swap
Size 24 KB
Load time 0 ms
Start 0 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+
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
Network Waterfall
54 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
76% of JavaScript execution is third-party
First-party Third-party 1034ms · 743KB · €11/mo
privacy.condenastdigital.com
Other
Costly
Execution 238ms
Transfer 198 KB
Monthly Cost €3/mo
cdn.arstechnica.net
Other
Costly
Execution 236ms
Transfer 71 KB
Unused 82%
Monthly Cost €3/mo
Unattributable
Other
Costly
Execution 206ms
Transfer 0 KB
Monthly Cost €2/mo
Google Tag Manager
Tag Manager
Optional
Execution 146ms
Transfer 173 KB
Unused 44%
Monthly Cost €2/mo
securepubads.g.doubleclick.net
Other
Optional
Execution 128ms
Transfer 182 KB
Unused 76%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 81ms
Transfer 118 KB
Unused 50%
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • privacy.condenastdigital.com adds 238ms and costs ~€3/month
  • cdn.arstechnica.net adds 236ms and costs ~€3/month
  • Unattributable adds 206ms and costs ~€2/month

76% 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

privacy.condenastdigital.com takes 238ms 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

cdn.arstechnica.net takes 236ms 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

82% of cdn.arstechnica.net's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

Unattributable takes 206ms 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

76% of securepubads.g.doubleclick.net's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

50% of Google Tag Manager's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

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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