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https://elifesciences.org

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
87
GRADE
B
FIX
0
REVIEW
6
PASS
9
INFO
2

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

Mobile Desktop
73
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
95
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.
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.

1.98 s

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

6.68 s

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

188 ms

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

0.011

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

1.98 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.

6.71 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 6 REVIEW
B
Page Weight Budget
1.0 MB transferred, 34 requests
REVIEW
1.0 MB transferred, 34 requests
Info::
Page weighs 2.4 MB (1.0 MB transferred)
Info::
Fonts are 246 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 246 KB
Info::
34 HTTP requests
Info::
Estimated 0.22 g CO2 per page load
1.0 MB / 2.4 MB budget
1.0 MB transferred
34 requests
0.22 g CO2 per page load
Images 488.2 KiB 45%
JavaScript 251.5 KiB 23%
Fonts 246.4 KiB 23%
CSS 44.6 KiB 4%
HTML 29.1 KiB 3%
Other 12.8 KiB 1%
Other 963 B 0%
Other 757 B 0%
0 2.4 MB 4.9 MB
Under budget

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

B
Third-Party Impact
48% third-party, 0 ms blocking
REVIEW
48% third-party, 0 ms blocking
Info::
Third-party code accounts for 48% of page weight (519.2 KiB of 1.0 MiB)
Info::
Third-party blocking time is low (0 ms)
52%
48%
First-party Third-party
C
Image Optimization
Action
19 images, 0 KB saveable
REVIEW
19 images, 0 KB saveable
Warning::
https://elifesciences.org/assets/patterns/img/patt... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://elifesciences.org/assets/images/investors/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://elifesciences.org/assets/patterns/img/patt... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://elifesciences.org/assets/images/investors/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://elifesciences.org/assets/images/investors/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://iiif.elifesciences.org/journal-cms/cover%2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://elifesciences.org/assets/images/investors/... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
19 images 488 KB
0 oversized -0 KB
17 legacy format
12 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

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

C
JS Execution Cost
Action
1321ms total JS execution
REVIEW
1321ms total JS execution
Warning::
https://elifesciences.org/: 427ms CPU time
Warning::
Unattributable: 358ms CPU time
Warning::
https://consent.cookiebot.com/uc.js: 351ms CPU time
Info::
https://elifesciences.org/assets/patterns/js/main....: 184ms CPU time
Warning::
Third-party scripts: 709ms (54% of total)

Main Thread Breakdown

Other 29% Script Evaluation 26% Style & Layout 24% Parse HTML & CSS 10% Script Parsing & Compilation 7% Rendering 4%
ScriptTotalScriptingParse/CompileParty
https://elifesciences.org/427ms7ms2ms1st
Unattributable358ms6ms0ms3rd
https://consent.cookiebot.com/uc.js351ms217ms11ms3rd
https://elifesciences.org/assets/patterns/js/main.5ed09a23.js184ms120ms57ms1st
B
JS Bundles
3 scripts, 101 KB unused
REVIEW
3 scripts, 101 KB unused
Warning::
https://elifesciences.org/assets/patterns/js/main....: 101 KB unused (72%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 101 KB
101 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://elifesciences.org/assets/patterns/js/main.5ed09a23.js141 KB101 KB (72%)✓1st
https://consent.cookiebot.com/uc.js27 KB—✓3rd
https://consent.cookiebot.com/0a5c50d8-fcf9-47b1-8f4f-1eaadb13941b/cc.js?renew=false&referer=elifesciences.org&dnt=false&init=false84 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

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
6 fonts (246 KB)
PASS
6 fonts (246 KB)
Info::
6 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

6

246 KB total

Render-blocking

0

of 6

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s 7.0 s FCP 2.0 s LCP 6.7 shttps://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2NotoSans-Regular-webfon... https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2 — 76.8 KiB — 21 ms — font-display: swaphttps://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2NotoSans-SemiBold-webfo... https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2 — 78.6 KiB — 22 ms — font-display: swaphttps://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2NotoSerif-Regular-webfo... https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2 — 91.0 KiB — 26 ms — font-display: swaphttps://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2NotoSans-Regular-webfon... https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2 — 0 B — 3 ms — font-display: swaphttps://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2NotoSans-SemiBold-webfo... https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2 — 0 B — 3 ms — font-display: swaphttps://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2NotoSerif-Regular-webfo... https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2 — 0 B — 3 ms — font-display: swap
NotoSans-Regular-webfon... woff2 swap
Size 77 KB
Load time 21 ms
Start 23 ms
Risk FOUT — text flashes from fallback to web font
NotoSans-SemiBold-webfo... woff2 swap
Size 79 KB
Load time 22 ms
Start 24 ms
Risk FOUT — text flashes from fallback to web font
NotoSerif-Regular-webfo... woff2 swap
Size 91 KB
Load time 26 ms
Start 25 ms
Risk FOUT — text flashes from fallback to web font
NotoSans-Regular-webfon... woff2 swap
Size 0 KB
Load time 3 ms
Start 151 ms
Risk FOUT — text flashes from fallback to web font
NotoSans-SemiBold-webfo... woff2 swap
Size 0 KB
Load time 3 ms
Start 151 ms
Risk FOUT — text flashes from fallback to web font
NotoSerif-Regular-webfo... woff2 swap
Size 0 KB
Load time 3 ms
Start 152 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
A
Page Weight Inventory
34 resources · 1.0 MB · 101 KB savings available
PASS
34 resources · 1.0 MB · 101 KB savings available
Warning::
Page weight 50 KB over 1MB target
Got: 1.0 MB Expected: ≤ 1 MB
Info::
~101 KB of savings available
Warning::
13 third-party resources (48% of weight)
34 resources · 1.0 MiB · 13 third-party 50.3 KiB over 1MB target
Image 47% · 501.0 KiB
JavaScript 23% · 251.5 KiB
Font 23% · 246.4 KiB
CSS 4% · 44.6 KiB
Document 3% · 29.1 KiB
Other 0% · 1.7 KiB

~101.5 KiB of savings available

Remove unused JavaScript: 101.5 KiB
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+
HTTP Caching
max-age=1800 (30 minutes)
PASS
max-age=1800 (30 minutes)
Info::
Cache-Control header is set
Got: max-age=1800, public, s-maxage=3720, stale-if-error=86400, stale-while-revalidate=43200
Info::
Effective TTL: 30 minutes (max-age=1800)
Info::
CDN TTL: 1 hour (s-maxage=3720)
Info::
ETag present — enables conditional (304) responses
Cache-Control

max-age=1800, public, s-maxage=3720, stale-if-error=86400, stale-while-revalidate=43200

DirectiveValueMeaning
max-age1800Cache for 30 minutes
public—Any cache may store this response
s-maxage3720CDN caches for 1 hour
stale-if-error86400
stale-while-revalidate43200Serve stale for 12 hours while fetching fresh
Effective TTL: 1800 seconds
Network Waterfall
34 requests over 457ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s 6.0 s 7.0 s FCP 2.0 s LCP 6.7 shttps://elifesciences.org// https://elifesciences.org/ — 200 — 28.4 KiB — 13 ms — h2https://elifesciences.org/assets/patterns/js/main.5ed09a23.js/assets/patterns/js/main.5ed09a23.j... https://elifesciences.org/assets/patterns/js/main.5ed09a23.js — 200 — 140.9 KiB — 26 ms — h2https://elifesciences.org/assets/patterns/css/all.d3600dff.css/assets/patterns/css/all.d3600dff.c... https://elifesciences.org/assets/patterns/css/all.d3600dff.css — 200 — 44.6 KiB — 17 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2/assets/patterns/fonts/NotoSans-Reg... https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2 — 200 — 76.8 KiB — 21 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2/assets/patterns/fonts/NotoSans-Sem... https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2 — 200 — 78.6 KiB — 22 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2/assets/patterns/fonts/NotoSerif-Re... https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2 — 200 — 91.0 KiB — 26 ms — h2https://consent.cookiebot.com/uc.jsconsent.cookiebot.com/uc.js https://consent.cookiebot.com/uc.js — 200 — 27.0 KiB — 77 ms — h2https://elifesciences.org/assets/patterns/img/patterns/organisms/elife-logo-home-page-xs.868c8bbb.svg/assets/patterns/img/patterns/organ... https://elifesciences.org/assets/patterns/img/patterns/organisms/elife-logo-home-page-xs.868c8bbb.svg — 200 — 1.5 KiB — 18 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F103503-a_striking_image.png/0,295,2592,1458/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F103503-a_striking_image.png/0,295,2592,1458/736,414/0/default.webp — 200 — 50.6 KiB — 193 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F673025v5_fig3s1-copy.jpg/0,99,1800,1013/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F673025v5_fig3s1-copy.jpg/0,99,1800,1013/736,414/0/default.webp — 200 — 55.3 KiB — 172 ms — h2https://consentcdn.cookiebot.com/consentconfig/0a5c50d8-fcf9-47b1-8f4f-1eaadb13941b/settings.jsonconsentcdn.cookiebot.com/consentcon... https://consentcdn.cookiebot.com/consentconfig/0a5c50d8-fcf9-47b1-8f4f-1eaadb13941b/settings.json — 200 — 963 B — 71 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F91082-a_striking_image-copy.jpg/0,373,2338,1316/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2F91082-a_striking_image-copy.jpg/0,373,2338,1316/736,414/0/default.webp — 200 — 142.0 KiB — 101 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-03%2Freviewed_preprint_mockup.png/0,100,1920,1080/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-03%2Freviewed_preprint_mockup.png/0,100,1920,1080/736,414/0/default.webp — 200 — 37.6 KiB — 103 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-03%2Fkamran_naim_pip_coen.jpg/967,0,4722,2656/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-03%2Fkamran_naim_pip_coen.jpg/967,0,4722,2656/736,414/0/default.webp — 200 — 32.5 KiB — 15 ms — h2https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2Fresearch-culture.jpeg/696,0,1609,905/736,414/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/cover%2F2026-04%2Fresearch-culture.jpeg/696,0,1609,905/736,414/0/default.webp — 200 — 76.7 KiB — 103 ms — h2https://iiif.elifesciences.org/journal-cms/person%2F2025-09%2Fpatrick-allard-from-source.jpg/0,0,512,512/320,/0/default.webpiiif.elifesciences.org/journal-cms/... https://iiif.elifesciences.org/journal-cms/person%2F2025-09%2Fpatrick-allard-from-source.jpg/0,0,512,512/320,/0/default.webp — 200 — 12.0 KiB — 14 ms — h2https://elifesciences.org/assets/patterns/img/patterns/organisms/elife-logo-xs.5a3c8c68.svg/assets/patterns/img/patterns/organ... https://elifesciences.org/assets/patterns/img/patterns/organisms/elife-logo-xs.5a3c8c68.svg — 200 — 1.5 KiB — 6 ms — h2https://elifesciences.org/assets/images/investors/hhmi.9d0951a2.svg/assets/images/investors/hhmi.9d095... https://elifesciences.org/assets/images/investors/hhmi.9d0951a2.svg — 200 — 3.0 KiB — 7 ms — h2https://elifesciences.org/assets/images/investors/wellcome.813f8634.svg/assets/images/investors/wellcome.8... https://elifesciences.org/assets/images/investors/wellcome.813f8634.svg — 200 — 1.4 KiB — 5 ms — h2https://elifesciences.org/assets/images/investors/max.a0546fd2.svg/assets/images/investors/max.a0546f... https://elifesciences.org/assets/images/investors/max.a0546fd2.svg — 200 — 8.6 KiB — 13 ms — h2https://elifesciences.org/assets/images/investors/kaw.db745e57.svg/assets/images/investors/kaw.db745e... https://elifesciences.org/assets/images/investors/kaw.db745e57.svg — 200 — 15.4 KiB — 15 ms — h2https://elifesciences.org/assets/patterns/img/patterns/molecules/carbon-neutral-organisation.b5ef3a77.png/assets/patterns/img/patterns/molec... https://elifesciences.org/assets/patterns/img/patterns/molecules/carbon-neutral-organisation.b5ef3a77.png — 200 — 48.9 KiB — 10 ms — h2https://consent.cookiebot.com/0a5c50d8-fcf9-47b1-8f4f-1eaadb13941b/cc.js?renew=false&referer=elifesciences.org&dnt=false&init=falseconsent.cookiebot.com/0a5c50d8-fcf9... https://consent.cookiebot.com/0a5c50d8-fcf9-47b1-8f4f-1eaadb13941b/cc.js?renew=false&referer=elifesciences.org&dnt=false&init=false — 200 — 83.6 KiB — 144 ms — h2https://elifesciences.org/assets/patterns/img/patterns/molecules/nav-primary-menu-ic.2e0832f2.svg/assets/patterns/img/patterns/molec... https://elifesciences.org/assets/patterns/img/patterns/molecules/nav-primary-menu-ic.2e0832f2.svg — 200 — 366 B — 4 ms — h2https://elifesciences.org/assets/patterns/img/icons/back-to-top.c3d6b554.svg/assets/patterns/img/icons/back-to-... https://elifesciences.org/assets/patterns/img/icons/back-to-top.c3d6b554.svg — 200 — 392 B — 2 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2/assets/patterns/fonts/NotoSans-Reg... https://elifesciences.org/assets/patterns/fonts/NotoSans-Regular-webfont-custom-2-subsetting.6031b15b.woff2 — 200 — 0 B — 3 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2/assets/patterns/fonts/NotoSans-Sem... https://elifesciences.org/assets/patterns/fonts/NotoSans-SemiBold-webfont-custom-2-subsetting.8b9e80d5.woff2 — 200 — 0 B — 3 ms — h2https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2/assets/patterns/fonts/NotoSerif-Re... https://elifesciences.org/assets/patterns/fonts/NotoSerif-Regular-webfont-custom-2-subsetting.e6069232.woff2 — 200 — 0 B — 3 ms — h2https://elifesciences.org/assets/patterns/img/icons/arrow-forward.3b0df237.svg/assets/patterns/img/icons/arrow-fo... https://elifesciences.org/assets/patterns/img/icons/arrow-forward.3b0df237.svg — 200 — 329 B — 3 ms — 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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
54% of JavaScript execution is third-party
First-party Third-party 709ms · 27KB · €8/mo
Unattributable
Other
Costly
Execution 358ms
Transfer 0 KB
Monthly Cost €4/mo
consent.cookiebot.com
Other
Costly
Execution 351ms
Transfer 27 KB
Monthly Cost €4/mo

These scripts may cost more than they're worth

  • Unattributable adds 358ms and costs ~€4/month
  • consent.cookiebot.com adds 351ms and costs ~€4/month

54% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

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Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

Unattributable takes 358ms 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

consent.cookiebot.com 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

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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