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https://sciencealert.com

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
73
GRADE
C
FIX
5
REVIEW
1
PASS
9
INFO
2

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

Mobile Desktop
28
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.
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.

1.97 s

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

12.19 s

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

890 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.854

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

3.53 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.

15.73 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
9 PASS 1 REVIEW 5 FIX
D
Page Weight Budget
Action
2.3 MB transferred, 68 requests
FIX
2.3 MB transferred, 68 requests
Info::
Page weighs 8.1 MB (2.3 MB transferred)
Warning::
JavaScript is 1.6 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.6 MB
Info::
68 HTTP requests
Info::
Estimated 0.49 g CO2 per page load
2.3 MB / 2.4 MB budget
2.3 MB transferred
68 requests
0.49 g CO2 per page load
JavaScript 1.6 MiB 67%
Images 645.1 KiB 27%
Fonts 56.5 KiB 2%
HTML 39.7 KiB 2%
CSS 20.0 KiB 1%
Other 17.0 KiB 1%
Other 10.2 KiB 0%
Other 2.4 KiB 0%
Other 561 B 0%
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
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (2.3 MiB of 2.3 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2983ms total JS execution
FIX
2983ms total JS execution
Warning::
https://www.sciencealert.com/: 449ms CPU time
Warning::
Unattributable: 423ms CPU time
Warning::
https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge....: 351ms CPU time
Warning::
https://cdn.privacy-mgmt.com/unified/4.40.1/usnat-...: 267ms CPU time
Info::
https://cdn.taboola.com/libtrc/sciencealert/loader...: 245ms CPU time
Warning::
Third-party scripts: 2983ms (100% of total)

Main Thread Breakdown

Script Evaluation 60% Script Parsing & Compilation 17% Other 12% Style & Layout 7%
ScriptTotalScriptingParse/CompileParty
https://www.sciencealert.com/449ms119ms11ms3rd
Unattributable423ms135ms0ms3rd
https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js351ms202ms141ms3rd
https://cdn.privacy-mgmt.com/unified/4.40.1/usnat-uspapi.090eccada574d39af6f8.bundle.js267ms235ms27ms3rd
https://cdn.taboola.com/libtrc/sciencealert/loader.js245ms136ms109ms3rd
https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353232ms146ms42ms3rd
https://bordeaux.futurecdn.net/bordeaux.js226ms157ms58ms3rd
https://scripts.clarity.ms/0.8.59/clarity.js209ms199ms7ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQ144ms105ms32ms3rd
https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.js137ms107ms14ms3rd

Showing top 10 of 14 scripts

F
JS Bundles
Action
24 scripts, 673 KB unused
FIX
24 scripts, 673 KB unused
Warning::
https://cdn.taboola.com/libtrc/sciencealert/loader...: 210 KB unused (65%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-VT6Z...: 114 KB unused (64%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://bordeaux.futurecdn.net/bordeaux.js: 90 KB unused (57%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.google.com/cse/static/element/dc329f57...: 70 KB unused (68%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-VT6Z...: 68 KB unused (38%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 673 KB
673 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://cdn.taboola.com/libtrc/sciencealert/loader.js324 KB210 KB (65%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353&cx=c&gtm=4e64h1178 KB114 KB (64%)✓3rd
https://bordeaux.futurecdn.net/bordeaux.js159 KB90 KB (57%)✓3rd
https://www.google.com/cse/static/element/dc329f57de078f5d/cse_element__en.js?usqp=CAM%3D103 KB70 KB (68%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353178 KB68 KB (38%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQ120 KB62 KB (52%)✓3rd
https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js256 KB38 KB (15%)✓3rd
https://www.sciencealert.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.129 KB21 KB (72%)✓3rd
https://cse.google.com/cse.js?cx=009882534323254498007:0ejrj_dbalc4 KB—✓3rd
https://scripts.clarity.ms/0.8.59/clarity.js26 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
Page Weight Inventory
Action
68 resources · 2.3 MB · 673 KB savings available
FIX
68 resources · 2.3 MB · 673 KB savings available
Warning::
Page weight 1.3 MB over 1MB target
Got: 2.3 MB Expected: ≤ 1 MB
Info::
~673 KB of savings available
Warning::
67 third-party resources (100% of weight)
Info::
2 resources over 200KB
68 resources · 2.3 MiB · 67 third-party 1.3 MiB over 1MB target
JavaScript 67% · 1.6 MiB
Image 27% · 646.3 KiB
Font 2% · 56.5 KiB
Document 2% · 42.2 KiB
Other 1% · 26.0 KiB
CSS 1% · 20.0 KiB

~673.4 KiB of savings available

Remove unused JavaScript: 673.4 KiB
B
Image Optimization
19 images, 0 KB saveable
REVIEW
19 images, 0 KB saveable
Info::
All images are well-optimized
19 images 645 KB
0 oversized -0 KB
5 legacy format
0 missing dimensions CLS risk
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 (57 KB)
PASS
2 fonts (57 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

57 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 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s FCP 2.0 s LCP 12.2 shttps://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff26xKydSBYKcSV-LCoeQqfX1R... https://fonts.gstatic.com/s/sourcesanspro/v23/6xKydSBYKcSV-LCoeQqfX1RYOo3i54rwlxdu3cOWxw.woff2 — 14.6 KiB — 73 ms — font-display: swaphttps://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2memvYaGs126MiZpBA-UvWbX... https://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2 — 42.0 KiB — 86 ms — font-display: swap
6xKydSBYKcSV-LCoeQqfX1R... woff2 swap
Size 15 KB
Load time 73 ms
Start 954 ms
Risk FOUT — text flashes from fallback to web font
memvYaGs126MiZpBA-UvWbX... woff2 swap
Size 42 KB
Load time 86 ms
Start 954 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
3 hints, 0 missing preconnects
PASS
3 hints, 0 missing preconnects
Info::
Page uses 3 resource hint(s)

Current Resource Hints

preconnect
1
preload
—
dns-prefetch
2
prefetch
—

3 resource hints configured

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

A
HTTP Caching
max-age=14400 (4 hours)
PASS
max-age=14400 (4 hours)
Info::
Cache-Control header is set
Got: public, max-age=14400
Info::
Effective TTL: 4 hours (max-age=14400)
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

public, max-age=14400

DirectiveValueMeaning
public—Any cache may store this response
max-age14400Cache for 4 hours
Effective TTL: 14400 seconds
Network Waterfall
68 requests over 2812ms
INFO
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s FCP 2.0 s LCP 12.2 shttps://sciencealert.com// https://sciencealert.com/ — 301 — 1019 B — 219 ms — h2https://www.sciencealert.com/www.sciencealert.com/ https://www.sciencealert.com/ — 200 — 37.4 KiB — 652 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQ — 200 — 120.1 KiB — 171 ms — h2https://www.clarity.ms/tag/otkbgpbwhiwww.clarity.ms/tag/otkbgpbwhi https://www.clarity.ms/tag/otkbgpbwhi — 200 — 855 B — 139 ms — http/1.1https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.jscdn.privacy-mgmt.com/unified/wrappe... https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.js — 200 — 40.4 KiB — 147 ms — h2https://www.sciencealert.com/wp-content/plugins/hm-gtm/assets/events.js?ver=3.1.3www.sciencealert.com/wp-content/plu... https://www.sciencealert.com/wp-content/plugins/hm-gtm/assets/events.js?ver=3.1.3 — 200 — 903 B — 27 ms — h2https://bordeaux.futurecdn.net/bordeaux.jsbordeaux.futurecdn.net/bordeaux.js https://bordeaux.futurecdn.net/bordeaux.js — 200 — 159.0 KiB — 210 ms — h2https://cdn.taboola.com/libtrc/sciencealert/loader.jscdn.taboola.com/libtrc/sciencealert... https://cdn.taboola.com/libtrc/sciencealert/loader.js — 200 — 323.9 KiB — 255 ms — h2https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js6093eccf-6734-4877-ac8b-83d6d0e27b4... https://6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app/6093eccf-6734-4877-ac8b-83d6d0e27b46-web.js — 200 — 255.5 KiB — 148 ms — h2https://freyr.futurecdn.net/freyr.jsfreyr.futurecdn.net/freyr.js https://freyr.futurecdn.net/freyr.js — 200 — 21.1 KiB — 161 ms — h2https://www.sciencealert.com/images/2026/04/teen-struggling-at-school-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/teen-struggling-at-school-768x432.jpg — 200 — 42.0 KiB — 581 ms — h2https://sb.scorecardresearch.com/beacon.jssb.scorecardresearch.com/beacon.js https://sb.scorecardresearch.com/beacon.js — 200 — 6.7 KiB — 144 ms — h2https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353www.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=G-VT6ZH45353 — 200 — 177.9 KiB — 77 ms — h2https://www.sciencealert.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.1www.sciencealert.com/wp-includes/js... https://www.sciencealert.com/wp-includes/js/jquery/jquery.min.js?ver=3.7.1 — 200 — 29.3 KiB — 38 ms — h2https://www.sciencealert.com/wp-includes/js/jquery/jquery-migrate.min.js?ver=3.4.1www.sciencealert.com/wp-includes/js... https://www.sciencealert.com/wp-includes/js/jquery/jquery-migrate.min.js?ver=3.4.1 — 200 — 4.9 KiB — 34 ms — h2https://cse.google.com/cse.js?cx=009882534323254498007:0ejrj_dbalccse.google.com/cse.js?cx=0098825343... https://cse.google.com/cse.js?cx=009882534323254498007:0ejrj_dbalc — 200 — 3.6 KiB — 124 ms — h2https://www.sciencealert.com/wp-content/themes/sciencealert/dist/js/subscription-form.min.js?ver=69920a1d4c0952312c2awww.sciencealert.com/wp-content/the... https://www.sciencealert.com/wp-content/themes/sciencealert/dist/js/subscription-form.min.js?ver=69920a1d4c0952312c2a — 200 — 1.8 KiB — 35 ms — h2https://www.sciencealert.com/wp-content/themes/sciencealert/dist/js/homepage.min.js?ver=2a801e325cc202644fbdwww.sciencealert.com/wp-content/the... https://www.sciencealert.com/wp-content/themes/sciencealert/dist/js/homepage.min.js?ver=2a801e325cc202644fbd — 200 — 2.6 KiB — 36 ms — h2https://www.sciencealert.com/images/2026/04/DNAHeader-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/DNAHeader-768x432.jpg — 200 — 31.6 KiB — 43 ms — h2https://www.sciencealert.com/images/2026/04/mars-dragonscale-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/mars-dragonscale-768x432.jpg — 200 — 69.6 KiB — 75 ms — h2https://www.sciencealert.com/images/2026/04/WhiteFronted-Nunbirds-in-the-Amazon-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/WhiteFronted-Nunbirds-in-the-Amazon-768x432.jpg — 200 — 44.4 KiB — 41 ms — h2https://www.sciencealert.com/images/2025/10/chronic_fatigue_bloodtest_header-738x415.jpgwww.sciencealert.com/images/2025/10... https://www.sciencealert.com/images/2025/10/chronic_fatigue_bloodtest_header-738x415.jpg — 200 — 14.2 KiB — 75 ms — h2https://www.sciencealert.com/images/2026/04/Hands-holding-phone-with-chatbot-on-screen-1-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/Hands-holding-phone-with-chatbot-on-screen-1-768x432.jpg — 200 — 23.1 KiB — 62 ms — h2https://www.sciencealert.com/images/2026/04/Smartwatch-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/Smartwatch-768x432.jpg — 200 — 21.1 KiB — 74 ms — h2https://www.sciencealert.com/images/2026/04/FlamesInZeroGravityComparedToOnEarth-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/FlamesInZeroGravityComparedToOnEarth-768x432.jpg — 200 — 11.4 KiB — 74 ms — h2https://www.sciencealert.com/images/2026/04/WomanHoldsEarInDiscomfort-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/WomanHoldsEarInDiscomfort-768x432.jpg — 200 — 39.5 KiB — 74 ms — h2https://www.sciencealert.com/images/2026/04/timey-wimey-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/timey-wimey-768x432.jpg — 200 — 110.0 KiB — 76 ms — h2https://www.sciencealert.com/images/2026/04/WomanSittingAloneOnHospitalBed-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/WomanSittingAloneOnHospitalBed-768x432.jpg — 200 — 22.2 KiB — 72 ms — h2https://www.sciencealert.com/images/2026/04/NasalSprayPurpleTonedOnBlack-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/NasalSprayPurpleTonedOnBlack-768x432.jpg — 200 — 26.4 KiB — 69 ms — h2https://www.sciencealert.com/images/2026/04/BolivianMummyTooth-768x432.jpgwww.sciencealert.com/images/2026/04... https://www.sciencealert.com/images/2026/04/BolivianMummyTooth-768x432.jpg — 200 — 44.6 KiB — 379 ms — h2
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s FCP 2.0 s LCP 12.2 shttps://sciencealert.com// https://sciencealert.com/ — 301 — 1019 B — 219 ms — h2https://www.sciencealert.com/www.sciencealert.com/ https://www.sciencealert.com/ — 200 — 37.4 KiB — 652 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-T9C3TSJQ — 200 — 120.1 KiB — 171 ms — h2https://www.clarity.ms/tag/otkbgpbwhiwww.clarity.ms/tag/otkbgpbwhi https://www.clarity.ms/tag/otkbgpbwhi — 200 — 855 B — 139 ms — http/1.1https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.jscdn.privacy-mgmt.com/unified/wrappe... https://cdn.privacy-mgmt.com/unified/wrapperMessagingWithoutDetection.js — 200 — 40.4 KiB — 147 ms — h2https://www.sciencealert.com/wp-content/plugins/hm-gtm/assets/events.js?ver=3.1.3www.sciencealert.com/wp-content/plu... https://www.sciencealert.com/wp-content/plugins/hm-gtm/assets/events.js?ver=3.1.3 — 200 — 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https://cdn.privacy-mgmt.com/Notice.30929.css — 200 — 6.7 KiB — 34 ms — h2https://cdn.privacy-mgmt.com/polyfills.01516.jscdn.privacy-mgmt.com/polyfills.0151... https://cdn.privacy-mgmt.com/polyfills.01516.js — 200 — 2.3 KiB — 35 ms — h2https://cdn.privacy-mgmt.com/Notice.8f529.jscdn.privacy-mgmt.com/Notice.8f529.j... https://cdn.privacy-mgmt.com/Notice.8f529.js — 200 — 91.2 KiB — 83 ms — h2https://www.sciencealert.com/images/2022/08/cropped-sa-rounded-favicon-32x32.pngwww.sciencealert.com/images/2022/08... https://www.sciencealert.com/images/2022/08/cropped-sa-rounded-favicon-32x32.png — 200 — 1.2 KiB — 42 ms — h2https://cdn.privacy-mgmt.com/consent/tcfv2/vendor-list/categories?siteId=35717cdn.privacy-mgmt.com/consent/tcfv2/... https://cdn.privacy-mgmt.com/consent/tcfv2/vendor-list/categories?siteId=35717 — 200 — 1.1 KiB — 47 ms — h2https://cdn.privacy-mgmt.com/consent/tcfv2/vendor-list/categories?siteId=35717&consentLanguage=encdn.privacy-mgmt.com/consent/tcfv2/... https://cdn.privacy-mgmt.com/consent/tcfv2/vendor-list/categories?siteId=35717&consentLanguage=en — 200 — 1.1 KiB — 46 ms — h2https://j.clarity.ms/collectj.clarity.ms/collect https://j.clarity.ms/collect — 204 — 284 B — 101 ms — http/1.1
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 2983ms · 1406KB · $40/mo
www.sciencealert.com
Other
Costly
Execution 449ms
Transfer 37 KB
Monthly Cost $6/mo
Unattributable
Other
Costly
Execution 423ms
Transfer 0 KB
Monthly Cost $6/mo
6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app
Other
Costly
Execution 351ms
Transfer 256 KB
Unused 15%
Monthly Cost $5/mo
cdn.privacy-mgmt.com
Other
Costly
Execution 267ms
Transfer 34 KB
Monthly Cost $4/mo
cdn.taboola.com
Other
Costly
Execution 245ms
Transfer 324 KB
Unused 65%
Monthly Cost $3/mo
Google Tag Manager
Tag Manager
Costly
Execution 232ms
Transfer 178 KB
Unused 38%
Monthly Cost $3/mo
bordeaux.futurecdn.net
Other
Costly
Execution 226ms
Transfer 159 KB
Unused 57%
Monthly Cost $3/mo
Microsoft Clarity
Session Replay
Costly
Execution 209ms
Transfer 26 KB
Monthly Cost $3/mo
Google Tag Manager
Tag Manager
Optional
Execution 144ms
Transfer 120 KB
Unused 52%
Monthly Cost $2/mo
cdn.privacy-mgmt.com
Other
Optional
Execution 137ms
Transfer 40 KB
Monthly Cost $2/mo
Google Tag Manager
Tag Manager
Optional
Execution 89ms
Transfer 178 KB
Unused 64%
Monthly Cost $1/mo
freyr.futurecdn.net
Other
Optional
Execution 77ms
Transfer 21 KB
Monthly Cost $1/mo
www.sciencealert.com
Other
Optional
Execution 73ms
Transfer 29 KB
Unused 72%
Monthly Cost $1/mo
cse.google.com
Other
Optional
Execution 60ms
Transfer 4 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.sciencealert.com adds 449ms and costs ~$6/month
  • Unattributable adds 423ms and costs ~$6/month
  • 6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app adds 351ms and costs ~$5/month
  • cdn.privacy-mgmt.com adds 267ms and costs ~$4/month
  • cdn.taboola.com adds 245ms and costs ~$3/month
  • Google Tag Manager adds 232ms and costs ~$3/month
  • bordeaux.futurecdn.net adds 226ms and costs ~$3/month
  • Microsoft Clarity adds 209ms 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.sciencealert.com takes 449ms 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 423ms 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

6093eccf-6734-4877-ac8b-83d6d0e27b46.edge.permutive.app takes 351ms 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.privacy-mgmt.com takes 267ms 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.taboola.com takes 245ms 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

65% of cdn.taboola.com'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

Google Tag Manager takes 232ms 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

bordeaux.futurecdn.net takes 226ms 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

57% of bordeaux.futurecdn.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

Microsoft Clarity takes 209ms 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

52% 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

64% 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

72% of www.sciencealert.com'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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