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Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
81
GRADE
B
FIX
4
REVIEW
3
PASS
8
INFO
2

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

Mobile Desktop
50
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
91
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.
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.

2.46 s

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

10.08 s

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

716 ms

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

0.000

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

5.42 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.

10.08 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
8 PASS 3 REVIEW 4 FIX
D
Third-Party Impact
Action
68% third-party, 0 ms blocking
FIX
68% third-party, 0 ms blocking
Warning::
Third-party code accounts for 68% of page weight (605.1 KiB of 895.9 KiB)
Info::
Third-party blocking time is low (0 ms)
32%
68%
First-party Third-party
D
JS Execution Cost
Action
2156ms total JS execution
FIX
2156ms total JS execution
Warning::
https://www.googletagmanager.com/gtag/js?id=G-CSLL...: 338ms CPU time
Warning::
https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/ji...: 316ms CPU time
Warning::
Unattributable: 303ms CPU time
Warning::
https://siteintercept.qualtrics.com/dxjsmodule/12....: 280ms CPU time
Info::
https://script.crazyegg.com/pages/versioned/common...: 244ms CPU time
Warning::
Third-party scripts: 1603ms (74% of total)

Main Thread Breakdown

Script Evaluation 66% Other 15% Script Parsing & Compilation 11% Style & Layout 6%
ScriptTotalScriptingParse/CompileParty
https://www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L338ms291ms44ms3rd
https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js316ms194ms67ms1st
Unattributable303ms10ms0ms3rd
https://siteintercept.qualtrics.com/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=www.ncbi.nlm.nih.gov280ms249ms14ms3rd
https://script.crazyegg.com/pages/versioned/common-scripts/4ce8c7df8d425cc50464576824ed91eb.js244ms212ms18ms3rd
https://www.googletagmanager.com/gtag/js?id=G-DP2X732JSX&l=pingerDataLayer&cx=c&gtm=4e64h1227ms190ms35ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer211ms176ms33ms3rd
https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/rlib/js/InstrumentOmnitureBaseJS/InstrumentNCBIConfigJS/InstrumentNCBIBaseJS/InstrumentPageStarterJS.js?v=1161ms73ms11ms1st
https://www.ncbi.nlm.nih.gov/75ms7ms3ms1st
D
JS Bundles
Action
17 scripts, 401 KB unused
FIX
17 scripts, 401 KB unused
Warning::
https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/ji...: 142 KB unused (78%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-DP2X...: 62 KB unused (42%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-CSLL...: 62 KB unused (42%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-PC9...: 60 KB unused (47%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://script.crazyegg.com/pages/versioned/common...: 30 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 401 KB
401 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js183 KB142 KB (78%)✓1st
https://www.googletagmanager.com/gtag/js?id=G-DP2X732JSX&l=pingerDataLayer&cx=c&gtm=4e64h1148 KB62 KB (42%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L147 KB62 KB (42%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer130 KB60 KB (47%)✓3rd
https://script.crazyegg.com/pages/versioned/common-scripts/4ce8c7df8d425cc50464576824ed91eb.js55 KB30 KB (54%)✓3rd
https://siteintercept.qualtrics.com/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=www.ncbi.nlm.nih.gov36 KB22 KB (63%)✓3rd
https://siteintercept.qualtrics.com/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprise31 KB22 KB (71%)✓3rd
https://zndikywqsjiuwn0q5-nlmenterprise.siteintercept.qualtrics.com/SIE/?Q_ZID=ZN_dikYWqsjiUWN0Q55 KB—✓3rd
https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/static/js/hfjs2.js5 KB—✗1st
https://dap.digitalgov.gov/Universal-Federated-Analytics-Min.js?agency=HHS&subagency=NCBI%20-%20ncbi.nlm.nih.gov&sitetopic=NCBI%20Pinger%200.39.3&siteplatform=NCBI%20Pinger%200.39.39 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.

C
Image Optimization
Action
20 images, 0 KB saveable
REVIEW
20 images, 0 KB saveable
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/sub... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/dow... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/dev... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/f... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/ana... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/img/c... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/lea... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/coreutils/nwds/img/lo... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.ncbi.nlm.nih.gov/home/images/icons/res... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
20 images 22 KB
0 oversized -0 KB
20 legacy format
9 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

B
Page Weight Inventory
55 resources · 896 KB · 401 KB savings available
REVIEW
55 resources · 896 KB · 401 KB savings available
Info::
Within 1MB page-weight target
Got: 896 KB
Info::
~401 KB of savings available
Warning::
22 third-party resources (68% of weight)
55 resources · 895.9 KiB · 22 third-party Within 1MB page-weight target
JavaScript 91% · 818.8 KiB
CSS 3% · 30.0 KiB
Image 3% · 26.0 KiB
Document 1% · 11.0 KiB
Other 1% · 10.1 KiB

~401.5 KiB of savings available

Remove unused JavaScript: 401.5 KiB
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A
Page Weight Budget
896 KB transferred, 55 requests
PASS
896 KB transferred, 55 requests
Info::
Page weighs 3.0 MB (896 KB transferred)
Warning::
JavaScript is 812 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 812 KB
Info::
55 HTTP requests
Info::
Estimated 0.18 g CO2 per page load
896 KB / 2.4 MB budget
896 KB transferred
55 requests
0.18 g CO2 per page load
JavaScript 812.3 KiB 91%
CSS 30.0 KiB 3%
Images 22.0 KiB 2%
Other 16.9 KiB 2%
HTML 9.5 KiB 1%
Other 4.0 KiB 0%
Other 1.2 KiB 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Under budget

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

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
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
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
Network Waterfall
55 requests over 1656ms
INFO
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s FCP 2.5 s LCP 10.1 shttps://www.ncbi.nlm.nih.gov// https://www.ncbi.nlm.nih.gov/ — 200 — 9.5 KiB — 402 ms — h2https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js/core/jig/1.15.6/js/jig.min.js https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js — 200 — 182.7 KiB — 404 ms — h2https://www.ncbi.nlm.nih.gov/home/components/normalize-css/normalize.css/home/components/normalize-css/norm... https://www.ncbi.nlm.nih.gov/home/components/normalize-css/normalize.css — 200 — 2.6 KiB — 106 ms — h2https://www.ncbi.nlm.nih.gov/home/components/ncbi-standards/standard_base.css/home/components/ncbi-standards/sta... https://www.ncbi.nlm.nih.gov/home/components/ncbi-standards/standard_base.css — 200 — 1.7 KiB — 106 ms — h2https://www.ncbi.nlm.nih.gov/home/new_grid.css/home/new_grid.css https://www.ncbi.nlm.nih.gov/home/new_grid.css — 200 — 327 B — 102 ms — h2https://www.ncbi.nlm.nih.gov/home/homepage.css/home/homepage.css https://www.ncbi.nlm.nih.gov/home/homepage.css — 200 — 838 B — 103 ms — h2https://www.ncbi.nlm.nih.gov/home/legacy/page.css/home/legacy/page.css https://www.ncbi.nlm.nih.gov/home/legacy/page.css — 200 — 8.9 KiB — 109 ms — h2https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/favicons/favicon-57.png/coreutils/uswds/img/favicons/favic... https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/favicons/favicon-57.png — 200 — 587 B — 107 ms — h2https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-dot-gov.svg/coreutils/uswds/img/icon-dot-gov.s... https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-dot-gov.svg — 200 — 427 B — 108 ms — h2https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-https.svg/coreutils/uswds/img/icon-https.svg https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-https.svg — 200 — 363 B — 290 ms — h2https://www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg/coreutils/nwds/img/logos/AgencyLog... https://www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg — 200 — 9.0 KiB — 290 ms — h2https://www.ncbi.nlm.nih.gov/home/images/icons/submit.svg/home/images/icons/submit.svg https://www.ncbi.nlm.nih.gov/home/images/icons/submit.svg — 200 — 459 B — 101 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/rlib/js/InstrumentOmnitureBaseJS/InstrumentNCBIConfigJS/InstrumentNCBIBaseJS/InstrumentPageStarterJS.js?v=1/portal/portal3rc.fcgi/rlib/js/Inst... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/rlib/js/InstrumentOmnitureBaseJS/InstrumentNCBIConfigJS/InstrumentNCBIBaseJS/InstrumentPageStarterJS.js?v=1 — 200 — 29.5 KiB — 106 ms — h2https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/css/jig.min.css/core/jig/1.15.6/css/jig.min.css https://www.ncbi.nlm.nih.gov/core/jig/1.15.6/css/jig.min.css — 200 — 15.7 KiB — 103 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/static/js/hfjs2.js/portal/portal3rc.fcgi/static/js/hf... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/static/js/hfjs2.js — 200 — 5.2 KiB — 118 ms — h2https://script.crazyegg.com/pages/scripts/0027/2050.jsscript.crazyegg.com/pages/scripts/0... https://script.crazyegg.com/pages/scripts/0027/2050.js — 200 — 2.7 KiB — 75 ms — h3https://www.ncbi.nlm.nih.gov/home/images/icons/download.svg/home/images/icons/download.svg https://www.ncbi.nlm.nih.gov/home/images/icons/download.svg — 200 — 456 B — 106 ms — h2https://www.ncbi.nlm.nih.gov/home/images/icons/learn.svg/home/images/icons/learn.svg https://www.ncbi.nlm.nih.gov/home/images/icons/learn.svg — 200 — 889 B — 104 ms — h2https://www.ncbi.nlm.nih.gov/home/images/icons/develop.svg/home/images/icons/develop.svg https://www.ncbi.nlm.nih.gov/home/images/icons/develop.svg — 200 — 435 B — 102 ms — h2https://www.ncbi.nlm.nih.gov/home/images/icons/analyze.svg/home/images/icons/analyze.svg https://www.ncbi.nlm.nih.gov/home/images/icons/analyze.svg — 200 — 3.7 KiB — 106 ms — h2https://www.ncbi.nlm.nih.gov/home/images/icons/research.svg/home/images/icons/research.svg https://www.ncbi.nlm.nih.gov/home/images/icons/research.svg — 200 — 993 B — 104 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayerwww.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer — 200 — 129.9 KiB — 159 ms — h2https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/angle-arrow-down-primary.svg/coreutils/uswds/img/angle-arrow-do... https://www.ncbi.nlm.nih.gov/coreutils/uswds/img/angle-arrow-down-primary.svg — 200 — 378 B — 101 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/2375536/portal/portal3rc.fcgi/4013172/img/... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/2375536 — 200 — 172 B — 104 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/12285/portal/portal3rc.fcgi/4013172/img/... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/12285 — 200 — 2.5 KiB — 105 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/218235/portal/portal3rc.fcgi/4013172/img/... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/218235 — 200 — 322 B — 105 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/218233/portal/portal3rc.fcgi/4013172/img/... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4013172/img/218233 — 200 — 175 B — 106 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/194600/img/12244/portal/portal3rc.fcgi/194600/img/1... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/194600/img/12244 — 200 — 362 B — 108 ms — h2https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4054678/img/3418709/portal/portal3rc.fcgi/4054678/img/... https://www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/4054678/img/3418709 — 200 — 311 B — 107 ms — h2https://www.ncbi.nlm.nih.gov/stat?HTTP_REFERER=&SELF_URL=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2F&browserheight=1958&browserwidth=981&colorDepth=24&connection_effectivetype=4g&connection_type=&cookieSize=0&cookieenabled=true&is_browser_supported=true&jsevent=render&jsloadtime=&jsperf_basePage=2&jsperf_connect=201&jsperf_dns=3&jsperf_navTimingNetworkMS=404&jsperf_navTimingRedirectCount=0&jsperf_navTimingType=navigate&jsperf_navType=0&jsperf_redirectCount=0&jsperf_ttfb=196&jsrendertime=&language_code=en-US&myncbi_signed_in=false&ncbi_algorithm=&ncbi_app=guide&ncbi_db=&ncbi_featured_srcdb=&ncbi_nwds=&ncbi_pcid=&ncbi_pdid=HomePage&ncbi_phid=15aa9bc300d819791776797222945SID&ncbi_program=&ncbi_timesinceload=24&ncbi_timesincenavstart=966&pagename=guide%3ANONE%3AHomePage%3ANONE&pinger_in_iframe=false&screenavailheight=823&screenavailwidth=412&screenheight=823&screenwidth=412&server=www.ncbi.nlm.nih.gov&sgSource=native&sgversion=0.42.0&sgversion_hotfix=0&sgversion_major=0&sgversion_minor=42&spa_index=0/stat?HTTP_REFERER=&SELF_URL=https%... https://www.ncbi.nlm.nih.gov/stat?HTTP_REFERER=&SELF_URL=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2F&browserheight=1958&browserwidth=981&colorDepth=24&connection_effectivetype=4g&connection_type=&cookieSize=0&cookieenabled=true&is_browser_supported=true&jsevent=render&jsloadtime=&jsperf_basePage=2&jsperf_connect=201&jsperf_dns=3&jsperf_navTimingNetworkMS=404&jsperf_navTimingRedirectCount=0&jsperf_navTimingType=navigate&jsperf_navType=0&jsperf_redirectCount=0&jsperf_ttfb=196&jsrendertime=&language_code=en-US&myncbi_signed_in=false&ncbi_algorithm=&ncbi_app=guide&ncbi_db=&ncbi_featured_srcdb=&ncbi_nwds=&ncbi_pcid=&ncbi_pdid=HomePage&ncbi_phid=15aa9bc300d819791776797222945SID&ncbi_program=&ncbi_timesinceload=24&ncbi_timesincenavstart=966&pagename=guide%3ANONE%3AHomePage%3ANONE&pinger_in_iframe=false&screenavailheight=823&screenavailwidth=412&screenheight=823&screenwidth=412&server=www.ncbi.nlm.nih.gov&sgSource=native&sgversion=0.42.0&sgversion_hotfix=0&sgversion_major=0&sgversion_minor=42&spa_index=0 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h2https://siteintercept.qualtrics.com/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprisesiteintercept.qualtrics.com/dxjsmod... https://siteintercept.qualtrics.com/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprise — 200 — 30.9 KiB — 28 ms — h2https://siteintercept.qualtrics.com/dxjsmodule/7.f7df015b06d8a90ce822.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprisesiteintercept.qualtrics.com/dxjsmod... https://siteintercept.qualtrics.com/dxjsmodule/7.f7df015b06d8a90ce822.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprise — 200 — 1.4 KiB — 30 ms — h2https://siteintercept.qualtrics.com/dxjsmodule/1.bc67e778235741631577.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprisesiteintercept.qualtrics.com/dxjsmod... https://siteintercept.qualtrics.com/dxjsmodule/1.bc67e778235741631577.chunk.js?Q_CLIENTVERSION=2.46.0&Q_CLIENTTYPE=web&Q_BRANDID=nlmenterprise — 200 — 7.1 KiB — 28 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
74% of JavaScript execution is third-party
First-party Third-party 1603ms · 516KB · $21/mo
Google Tag Manager
Tag Manager
Costly
Execution 338ms
Transfer 147 KB
Unused 42%
Monthly Cost $4/mo
Unattributable
Other
Costly
Execution 303ms
Transfer 0 KB
Monthly Cost $4/mo
siteintercept.qualtrics.com
Other
Costly
Execution 280ms
Transfer 36 KB
Unused 63%
Monthly Cost $4/mo
script.crazyegg.com
Other
Costly
Execution 244ms
Transfer 55 KB
Unused 54%
Monthly Cost $3/mo
Google Tag Manager
Tag Manager
Costly
Execution 227ms
Transfer 148 KB
Unused 42%
Monthly Cost $3/mo
Google Tag Manager
Tag Manager
Costly
Execution 211ms
Transfer 130 KB
Unused 47%
Monthly Cost $3/mo

These scripts may cost more than they're worth

  • Google Tag Manager adds 338ms and costs ~$4/month
  • Unattributable adds 303ms and costs ~$4/month
  • siteintercept.qualtrics.com adds 280ms and costs ~$4/month
  • script.crazyegg.com adds 244ms and costs ~$3/month
  • Google Tag Manager adds 227ms and costs ~$3/month
  • Google Tag Manager adds 211ms and costs ~$3/month

74% 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

Google Tag Manager takes 338ms 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 303ms 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

siteintercept.qualtrics.com takes 280ms 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

63% of siteintercept.qualtrics.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

script.crazyegg.com takes 244ms 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

54% 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

Google Tag Manager 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

Google Tag Manager takes 211ms 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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