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https://medrxiv.org

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
85
GRADE
B
FIX
3
REVIEW
3
PASS
9
INFO
2

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

Mobile Desktop
54
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
88
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
81
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.

3.29 s

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

5.01 s

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

232 ms

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

0.330

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

3.29 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.

8.71 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 3 REVIEW 3 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 (703.9 KiB of 704.4 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Bundles
Action
12 scripts, 232 KB unused
FIX
12 scripts, 232 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-P4H...: 66 KB unused (59%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-0K57...: 63 KB unused (44%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_...: 53 KB unused (66%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://script.crazyegg.com/pages/versioned/common...: 29 KB unused (53%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.medrxiv.org/sites/default/files/advagg...: 22 KB unused (37%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.medrxiv.org/sites/default/files/advagg...: unminified — 12 KB could be saved
Info::
Total unused JavaScript: 232 KB
232 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-P4HH5NV113 KB66 KB (59%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-0K57TCX5BY144 KB63 KB (44%)✓3rd
https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_medrxiv.js80 KB53 KB (66%)✓3rd
https://script.crazyegg.com/pages/versioned/common-scripts/4ce8c7df8d425cc50464576824ed91eb.js55 KB29 KB (53%)✓3rd
https://www.medrxiv.org/sites/default/files/advagg_js/js__pLr-NK78ay59QifmKNmtslpYXxsCjzX3lUbvd1UscTE__ctlBAO9WIoTeHrrkcED2ker--5jOcIwlVrRRDIzReSI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js59 KB22 KB (37%)✗3rd
https://www.medrxiv.org/sites/default/files/advagg_js/js__bnwyEQSuZLC-kZnFqCi5iE02nOCzM7DjY7zYxcN9nsQ__VBiBT_qq_eHMMO2Q1rXK1u-hHff31XLUkmi9dgjuPeY__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js2 KB—✓3rd
https://www.medrxiv.org/sites/default/files/advagg_js/js__BmqjBnkz3MgYCAoc25s1lDRMEjLhC3mEPVonUFIHi08__Unwv5-ZIuHBfFwytsjEx1niBVJ7n1T4lPws7VrkHXM4__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js5 KB—✓3rd
https://rum-static.pingdom.net/prum.min.js3 KB—✓3rd
https://www.medrxiv.org/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js?14 KB—✓3rd
https://script.crazyegg.com/pages/scripts/0056/6375.js3 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
3 images, 0 KB saveable
REVIEW
3 images, 0 KB saveable
Warning::
https://www.medrxiv.org/sites/default/files/medRxi... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
3 images 44 KB
0 oversized -0 KB
3 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
1578ms total JS execution
REVIEW
1578ms total JS execution
Warning::
https://www.medrxiv.org/sites/default/files/advagg...: 333ms CPU time
Warning::
https://script.crazyegg.com/pages/versioned/common...: 296ms CPU time
Warning::
https://www.medrxiv.org/: 276ms CPU time
Info::
https://www.medrxiv.org/cdn-cgi/challenge-platform...: 227ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-0K57...: 185ms CPU time
Warning::
Third-party scripts: 1578ms (100% of total)

Main Thread Breakdown

Script Evaluation 59% Other 17% Style & Layout 11% Script Parsing & Compilation 7% Parse HTML & CSS 3%
ScriptTotalScriptingParse/CompileParty
https://www.medrxiv.org/sites/default/files/advagg_js/js__pLr-NK78ay59QifmKNmtslpYXxsCjzX3lUbvd1UscTE__ctlBAO9WIoTeHrrkcED2ker--5jOcIwlVrRRDIzReSI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js333ms223ms16ms3rd
https://script.crazyegg.com/pages/versioned/common-scripts/4ce8c7df8d425cc50464576824ed91eb.js296ms254ms21ms3rd
https://www.medrxiv.org/276ms32ms6ms3rd
https://www.medrxiv.org/cdn-cgi/challenge-platform/scripts/jsd/main.js227ms217ms3ms3rd
https://www.googletagmanager.com/gtag/js?id=G-0K57TCX5BY185ms151ms33ms3rd
Unattributable159ms6ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-P4HH5NV102ms68ms33ms3rd
B
Page Weight Inventory
37 resources · 704 KB · 232 KB savings available
REVIEW
37 resources · 704 KB · 232 KB savings available
Info::
Within 1MB page-weight target
Got: 704 KB
Info::
~232 KB of savings available
Warning::
36 third-party resources (100% of weight)
37 resources · 704.4 KiB · 36 third-party Within 1MB page-weight target
JavaScript 68% · 478.5 KiB
CSS 17% · 117.4 KiB
Image 7% · 48.4 KiB
Font 6% · 43.2 KiB
Document 2% · 11.7 KiB
Other 1% · 5.3 KiB

~232.5 KiB of savings available

Remove unused JavaScript: 232.5 KiB
A+
Page Weight Budget
704 KB transferred, 37 requests
PASS
704 KB transferred, 37 requests
Info::
Page weighs 1.7 MB (704 KB transferred)
Info::
37 HTTP requests
Info::
Estimated 0.14 g CO2 per page load
704 KB / 2.4 MB budget
704 KB transferred
37 requests
0.14 g CO2 per page load
JavaScript 478.5 KiB 68%
CSS 117.4 KiB 17%
Images 43.5 KiB 6%
Fonts 43.2 KiB 6%
HTML 10.4 KiB 1%
Other 5.5 KiB 1%
Other 5.3 KiB 1%
Other 550 B 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+
Font Loading
1 fonts (43 KB)
PASS
1 fonts (43 KB)
Info::
1 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

1

43 KB total

Render-blocking

0

of 1

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 FCP 3.3 s LCP 5.0 shttps://www.medrxiv.org/sites/all/themes/highwire/jcore_1/font/fontawesome-webfont.woff?v=3.2.1fontawesome-webfont.woff https://www.medrxiv.org/sites/all/themes/highwire/jcore_1/font/fontawesome-webfont.woff?v=3.2.1 — 43.2 KiB — 70 ms — font-display: swap
fontawesome-webfont.woff unknown swap
Size 43 KB
Load time 70 ms
Start 682 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)

Fixing the unchecked items could save ~13 KB and ~26 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+
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

Network Waterfall
37 requests over 2294ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 3.3 s LCP 5.0 shttps://medrxiv.org// https://medrxiv.org/ — 302 — 433 B — 231 ms — h2https://www.medrxiv.org/www.medrxiv.org/ https://www.medrxiv.org/ — 200 — 10.4 KiB — 339 ms — h2https://www.medrxiv.org/sites/default/files/advagg_css/css__HZ-qMUtEfy3t2_CcrU8XBY06UykWM66UEaEJRxHJjoU__PepE_YD5_fPaq_q4kYw-iLGcWZIguFkT5KAZEo4NcWM__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.csswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_css/css__HZ-qMUtEfy3t2_CcrU8XBY06UykWM66UEaEJRxHJjoU__PepE_YD5_fPaq_q4kYw-iLGcWZIguFkT5KAZEo4NcWM__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.css — 200 — 10.4 KiB — 26 ms — h2https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.7.2/css/all.min.csscdn.jsdelivr.net/npm/@fortawesome/f... https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.7.2/css/all.min.css — 200 — 22.1 KiB — 42 ms — h2https://www.medrxiv.org/sites/default/files/advagg_css/css__vP96nkAt3EeLU62QRdHXKZuS9tqQ1EMDJC_PSKd7hEk__-QNIdNeGmHVz1SZAaU0zPbKgZqousY6M-qJrXXnrKKA__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.csswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_css/css__vP96nkAt3EeLU62QRdHXKZuS9tqQ1EMDJC_PSKd7hEk__-QNIdNeGmHVz1SZAaU0zPbKgZqousY6M-qJrXXnrKKA__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.css — 200 — 18.9 KiB — 34 ms — h2https://www.medrxiv.org/sites/default/files/advagg_css/css__Emt7SSsxOn34QjMVwnu4g8XjLLv_S0JbH48g5-BKf1c__1DRWXQzAoLHKAicR_9AnF1-uoid-Dmi1-kB07HSe-7k__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.csswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_css/css__Emt7SSsxOn34QjMVwnu4g8XjLLv_S0JbH48g5-BKf1c__1DRWXQzAoLHKAicR_9AnF1-uoid-Dmi1-kB07HSe-7k__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.css — 200 — 9.1 KiB — 31 ms — h2https://www.medrxiv.org/sites/default/files/advagg_css/css__2WBMox6sOrN42ss5lCnH7WWVRdFdJCxtTKnQJYRwTE4__yqNvNYLvMpjy3ffuJrjjm9uW2i-Me1c23KLYuWHaqio__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.csswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_css/css__2WBMox6sOrN42ss5lCnH7WWVRdFdJCxtTKnQJYRwTE4__yqNvNYLvMpjy3ffuJrjjm9uW2i-Me1c23KLYuWHaqio__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.css — 200 — 13.0 KiB — 29 ms — h2https://www.medrxiv.org/sites/default/files/advagg_css/css__oMKaN562ROZEhY5bedOfJGaPkvKlrukVNVo2XkRWD9Y__hsiFRyI4A0SybrSkkCu9HSGtJ5hlTlGSn5bEIYP8DoI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.csswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_css/css__oMKaN562ROZEhY5bedOfJGaPkvKlrukVNVo2XkRWD9Y__hsiFRyI4A0SybrSkkCu9HSGtJ5hlTlGSn5bEIYP8DoI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.css — 200 — 2.2 KiB — 28 ms — h2https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_medrxiv.cssd33xdlntwy0kbs.cloudfront.net/cshl_... https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_medrxiv.css — 200 — 41.7 KiB — 51 ms — http/1.1https://www.medrxiv.org/sites/default/files/advagg_js/js__pLr-NK78ay59QifmKNmtslpYXxsCjzX3lUbvd1UscTE__ctlBAO9WIoTeHrrkcED2ker--5jOcIwlVrRRDIzReSI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.jswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_js/js__pLr-NK78ay59QifmKNmtslpYXxsCjzX3lUbvd1UscTE__ctlBAO9WIoTeHrrkcED2ker--5jOcIwlVrRRDIzReSI__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js — 200 — 59.2 KiB — 45 ms — h2https://www.medrxiv.org/sites/default/files/medrxiv_inner_logo.pngwww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/medrxiv_inner_logo.png — 200 — 11.4 KiB — 31 ms — h2https://www.medrxiv.org/sites/default/files/medRxiv_homepage_logo.pngwww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/medRxiv_homepage_logo.png — 200 — 31.2 KiB — 197 ms — h2https://www.medrxiv.org/sites/default/files/advagg_js/js__bnwyEQSuZLC-kZnFqCi5iE02nOCzM7DjY7zYxcN9nsQ__VBiBT_qq_eHMMO2Q1rXK1u-hHff31XLUkmi9dgjuPeY__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.jswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_js/js__bnwyEQSuZLC-kZnFqCi5iE02nOCzM7DjY7zYxcN9nsQ__VBiBT_qq_eHMMO2Q1rXK1u-hHff31XLUkmi9dgjuPeY__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js — 200 — 1.7 KiB — 36 ms — h3https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_medrxiv.jsd33xdlntwy0kbs.cloudfront.net/cshl_... https://d33xdlntwy0kbs.cloudfront.net/cshl_custom_medrxiv.js — 200 — 80.4 KiB — 6 ms — http/1.1https://www.medrxiv.org/sites/default/files/advagg_js/js__BmqjBnkz3MgYCAoc25s1lDRMEjLhC3mEPVonUFIHi08__Unwv5-ZIuHBfFwytsjEx1niBVJ7n1T4lPws7VrkHXM4__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.jswww.medrxiv.org/sites/default/files... https://www.medrxiv.org/sites/default/files/advagg_js/js__BmqjBnkz3MgYCAoc25s1lDRMEjLhC3mEPVonUFIHi08__Unwv5-ZIuHBfFwytsjEx1niBVJ7n1T4lPws7VrkHXM4__QrrGUc7CpljPR5Aph-ukPbcwtK4AWrHGwCEXJ_k1V_c.js — 200 — 4.9 KiB — 35 ms — h3https://www.googletagmanager.com/gtag/js?id=G-0K57TCX5BYwww.googletagmanager.com/gtag/js?id... https://www.googletagmanager.com/gtag/js?id=G-0K57TCX5BY — 200 — 143.9 KiB — 135 ms — h2https://rum-static.pingdom.net/prum.min.jsrum-static.pingdom.net/prum.min.js https://rum-static.pingdom.net/prum.min.js — 200 — 2.8 KiB — 62 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-P4HH5NVwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-P4HH5NV — 200 — 113.2 KiB — 1.1 s — h2https://www.medrxiv.org/sites/all/themes/highwire/jcore_1/font/fontawesome-webfont.woff?v=3.2.1www.medrxiv.org/sites/all/themes/hi... https://www.medrxiv.org/sites/all/themes/highwire/jcore_1/font/fontawesome-webfont.woff?v=3.2.1 — 200 — 43.2 KiB — 70 ms — h3https://www.medrxiv.org/highwire/sub-datawww.medrxiv.org/highwire/sub-data https://www.medrxiv.org/highwire/sub-data — 200 — 820 B — 490 ms — h3https://img.icons8.com/color/16/000000/google-logo.pngimg.icons8.com/color/16/000000/goog... https://img.icons8.com/color/16/000000/google-logo.png — 200 — 998 B — 144 ms — h2https://www.medrxiv.org/cdn-cgi/challenge-platform/scripts/jsd/main.jswww.medrxiv.org/cdn-cgi/challenge-p... https://www.medrxiv.org/cdn-cgi/challenge-platform/scripts/jsd/main.js — 302 — 223 B — 22 ms — h3https://www.medrxiv.org/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js?www.medrxiv.org/cdn-cgi/challenge-p... https://www.medrxiv.org/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js? — 200 — 14.2 KiB — 28 ms — h3https://www.medrxiv.org/cdn-cgi/challenge-platform/h/b/jsd/oneshot/0b8fb825cb67/0.7989566937318935:1776802399:zTKHR5rhRQnoOcPGrKEmCIpeWlJ-83Z6Gei8kRIaJDY/9eff5a70c979d61dwww.medrxiv.org/cdn-cgi/challenge-p... 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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
100% of JavaScript execution is third-party
First-party Third-party 1578ms · 382KB · $21/mo
www.medrxiv.org
Other
Costly
Execution 333ms
Transfer 59 KB
Unused 37%
Monthly Cost $4/mo
script.crazyegg.com
Other
Costly
Execution 296ms
Transfer 55 KB
Unused 53%
Monthly Cost $4/mo
www.medrxiv.org
Other
Costly
Execution 276ms
Transfer 10 KB
Monthly Cost $4/mo
www.medrxiv.org
Other
Costly
Execution 227ms
Transfer 0 KB
Monthly Cost $3/mo
Google Tag Manager
Tag Manager
Optional
Execution 185ms
Transfer 144 KB
Unused 44%
Monthly Cost $2/mo
Unattributable
Other
Optional
Execution 159ms
Transfer 0 KB
Monthly Cost $2/mo
Google Tag Manager
Tag Manager
Optional
Execution 102ms
Transfer 113 KB
Unused 59%
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.medrxiv.org adds 333ms and costs ~$4/month
  • script.crazyegg.com adds 296ms and costs ~$4/month
  • www.medrxiv.org adds 276ms and costs ~$4/month
  • www.medrxiv.org adds 227ms 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.medrxiv.org takes 333ms 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

script.crazyegg.com takes 296ms 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

53% of script.crazyegg.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

www.medrxiv.org takes 276ms 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

www.medrxiv.org takes 227ms 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

59% 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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