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Lighthouse Mobile

· 0 checks — Mobile Lighthouse audit -- Performance, Accessibility, Best Practices, and SEO category breakdown.
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Detailed Report

Audit breakdown by category with detailed findings.

48

Performance

Insights

Remove large, duplicate JavaScript modules from bundles to reduce unnecessary bytes consumed by network activity.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Polyfills and transforms enable older browsers to use new JavaScript features. However, many aren't necessary for modern browsers. Consider modifying your JavaScript build process to not transpile Baseline features, unless you know you must support older browsers. Learn why most sites can deploy ES6+ code without transpiling

Why this matters

Performance issues directly impact user engagement and conversion rates.

3rd party code can significantly impact load performance. Reduce and defer loading of 3rd party code to prioritize your page's content.

Why this matters

Performance issues directly impact user engagement and conversion rates.

A long cache lifetime can speed up repeat visits to your page. Learn more about caching.

Why this matters

Performance issues directly impact user engagement and conversion rates.

RequestCache TTLTransfer Size
/sites/default/files/styles/large/public/2026-04/Kart-144...0.0 ms237.7 KiB
/sites/default/files/styles/large/public/2026-04/ATLAS_co...0.0 ms100.3 KiB
/sites/default/files/styles/large/public/2026-03/Toponium...0.0 ms91.9 KiB
/sites/default/files/styles/large/public/2026-04/collisio...0.0 ms62.8 KiB
/sites/default/files/styles/large/public/2026-03/Mosaic_s...0.0 ms32.3 KiB
/sites/default/files/styles/large/public/2026-04/IMG_7455...0.0 ms30.5 KiB
/sites/default/files/styles/large/public/2026-03/202603-0...0.0 ms20.1 KiB
/sites/default/files/styles/large/public/2026-03/Image_Ch...0.0 ms16.7 KiB

Your first network request is the most important. Reduce its latency by avoiding redirects, ensuring a fast server response, and enabling text compression.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Consider setting font-display to swap or optional to ensure text is consistently visible. swap can be further optimized to mitigate layout shifts with font metric overrides.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLEst Savings
framework.web.cern.ch/framework/3.0/fonts/open-sans/bold.woff265 ms
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/light.woff265 ms
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/bold.woff265 ms
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/regular.woff260 ms
framework.web.cern.ch/framework/3.0/fonts/cern/cern.woff260 ms
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/semibold.woff260 ms

A forced reflow occurs when JavaScript queries geometric properties (such as offsetWidth) after styles have been invalidated by a change to the DOM state. This can result in poor performance. Learn more about forced reflows and possible mitigations.

Why this matters

Performance issues directly impact user engagement and conversion rates.

headings: [map[key:source label:Top function call valueType:source-location] map[granularity:1 key:reflowTime label:Total reflow time valueType:ms]]
items: [map[reflowTime:24.179 source:map[column:22 line:19 type:source-location url:https://home.cern/core/misc/drupal.init.js?v=10.4.5 urlProvider:network]]]
headings: [map[key:source label:Source valueType:source-location] map[granularity:1 key:reflowTime label:Total reflow time valueType:ms]]
items: [map[reflowTime:40.227 source:map[column:14526 line:2 type:source-location url:https://framework.web.cern.ch/framework/3.0/js/scroll-magic/ScrollMagic.min.js urlProvider:network]] map[reflowTime:13.425 source:map[column:79427 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:2.239 source:map[column:20 line:1273 type:source-location url:https://framework.web.cern.ch/framework/3.0/js/owlcarousel/js/owl.carousel.js urlProvider:network]] map[reflowTime:7.341 source:map[column:49615 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:0.3 source:map[column:50335 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:0.211 source:map[column:50393 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:0.189 source:map[column:50457 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:0.127 source:map[column:49637 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]] map[reflowTime:0.347 source:map[column:51395 line:1 type:source-location url:https://home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 urlProvider:network]]]

Reducing the download time of images can improve the perceived load time of the page and LCP. Learn more about optimizing image size

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLResource SizeEst Savings
div.owl-stage > div.owl-item > div.header-block > div.background-component div.owl-stage > div.owl-item > div.header-block > div.background-component
home.cern/sites/default/files/2026-04/ALICE.png6.1 MiB5.1 MiB
div.owl-stage > div.owl-item > div.header-block > div.background-component div.owl-stage > div.owl-item > div.header-block > div.background-component
home.cern/sites/default/files/2026-04/Antimatter-3.png5.0 MiB4.0 MiB
Plan your CERN visit div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--17
home.cern/sites/default/files/2025-12/202310-230_50_2_1.jpg1.1 MiB868.3 KiB
div.owl-stage > div.owl-item > div.header-block > div.background-component div.owl-stage > div.owl-item > div.header-block > div.background-component
home.cern/sites/default/files/2026-04/Toponium.png1.3 MiB275.0 KiB
W and Z bosons div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--32
home.cern/sites/default/files/2025-12/69576_1.jpeg426.7 KiB218.7 KiB
CERN levels up with new superconducting karts Engineering News 1 April, 2026 carousel-cern-item.owl-item > div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--6
/sites/default/files/styles/large/public/2026-04/Kart-144...237.5 KiB212.9 KiB
Neutral currents div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--33
home.cern/sites/default/files/2025-12/60100_2.jpeg300.3 KiB202.0 KiB
CERN and the environment div#explore-cern > div.component-row__row > div.component-row__column > div#preview-card--20
home.cern/sites/default/files/2025-12/OPEN-PHO-CIVIL-2023-001-6_0_1.jpeg150.1 KiB105.6 KiB
ATLAS acts as a cosmic-ray laboratory Physics News 21 April, 2026 carousel-cern-item.owl-item > div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card
/sites/default/files/styles/large/public/2026-04/ATLAS_co...100.1 KiB79.0 KiB
CMS strengthens the case for toponium Physics News 25 March, 2026 carousel-cern-item.owl-item > div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--8
/sites/default/files/styles/large/public/2026-03/Toponium...91.8 KiB70.7 KiB
Take an immersive tour of CERN's accelerators... div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--18
home.cern/sites/default/files/2025-12/Screenshot-vitual-tour_1.jpg92.2 KiB61.9 KiB
CMS looks deep inside quarks Physics News 16 April, 2026 carousel-cern-item.owl-item > div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--3
/sites/default/files/styles/large/public/2026-04/collisio...62.6 KiB41.5 KiB
home div.site-info > div.site-info__logo > a > img
home.cern/sites/default/files/logo/cern-logo.png19.6 KiB17.2 KiB
The Large Hadron Collider div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--29
home.cern/sites/default/files/2025-12/CERN-AC-0911188-01_2.jpg45.3 KiB11.0 KiB
Explore CERN's educational resources div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--19
/sites/default/files/2025-12/Artist Rasheedah Phillips fr...263.8 KiB10.6 KiB
The Higgs boson div.component-row__row > div.component-row__column > div.box-effects-wrapper > div#preview-card--28
home.cern/sites/default/files/2025-12/ATLAS-PHO-EVENTS-2014-010-1_1.jpg43.2 KiB5.7 KiB
CERN to host Europe’s flagship open access pu... At CERN News 26 March, 2026 carousel-cern-item.owl-item > div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--7
/sites/default/files/styles/large/public/2026-03/Mosaic_s...32.1 KiB4.1 KiB

Optimize LCP by making the LCP image discoverable from the HTML immediately, and avoiding lazy-loading

Why this matters

Performance issues directly impact user engagement and conversion rates.

lhId: page-3-DIV
nodeLabel: div.owl-stage > div.owl-item > div.header-block > div.background-component
path: 1,HTML,1,BODY,4,MAIN,1,DIV,0,DIV,0,DIV,2,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,2,DIV,0,DIV,2,DIV
selector: div.owl-stage > div.owl-item > div.header-block > div.background-component
snippet: <div class="background-component background__image" style="">

HTTP/2 and HTTP/3 offer many benefits over HTTP/1.1, such as multiplexing. Learn more about using modern HTTP.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLProtocol
home.cern/http/1.1
home.cern/modules/custom/cern-loading/css/cern_loading.css?tckkx1http/1.1
framework.web.cern.ch/framework/3.0/js/owlcarousel/css/owl.carousel.csshttp/1.1
framework.web.cern.ch/framework/3.0/js/owlcarousel/css/owl.theme.default.csshttp/1.1
home.cern/core/misc/components/progress.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/align.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/fieldgroup.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/container-inline.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/clearfix.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/details.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/hidden.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/item-list.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/js.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/nowrap.module.css?tckkx1http/1.1
/core/modules/system/css/components/position-container.mo...http/1.1
home.cern/core/modules/system/css/components/reset-appearance.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/resize.module.css?tckkx1http/1.1
home.cern/core/modules/system/css/components/system-status-counter.css?tckkx1http/1.1
/core/modules/system/css/components/system-status-report-...http/1.1
/core/modules/system/css/components/system-status-report-...http/1.1
home.cern/core/modules/system/css/components/tablesort.module.css?tckkx1http/1.1
home.cern/modules/custom/cern-toolbar/assets/css/screen.css?tckkx1http/1.1
home.cern/modules/custom/cern-toolbar/assets/css/cookieconsent.css?tckkx1http/1.1
/modules/custom/cern-components/patterns/molecules/agenda...http/1.1
/modules/custom/cern-components/patterns/atoms/background...http/1.1
/modules/custom/cern-components/patterns/molecules/header...http/1.1
/modules/custom/cern-components/patterns/molecules/header...http/1.1
/modules/custom/cern-components/patterns/molecules/margin...http/1.1
/modules/custom/cern-components/patterns/molecules/menu/c...http/1.1
/modules/custom/cern-components/patterns/molecules/previe...http/1.1
/modules/custom/cern-components/patterns/molecules/row/cs...http/1.1
home.cern/core/modules/views/css/views.module.css?tckkx1http/1.1
home.cern/core/modules/layout_discovery/layouts/onecol/onecol.css?tckkx1http/1.1
home.cern/modules/contrib/paragraphs/css/paragraphs.unpublished.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/base.css?tckkx1http/1.1
home.cern/sites/default/files/color/cernpublic-ac827e9a/colors.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/layout.css?tckkx1http/1.1
framework.web.cern.ch/framework/3.0/js/prism/prism.csshttp/1.1
home.cern/sites/default/themes/custom/cernbase/css/components/footer.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/components/header.css?tckkx1http/1.1
/sites/default/themes/custom/cernbase/css/components/pagi...http/1.1
home.cern/sites/default/themes/custom/cernbase/css/components/forms.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/components/fields.css?tckkx1http/1.1
/sites/default/themes/custom/cernbase/css/components/drop...http/1.1
/sites/default/themes/custom/cernbase/css/components/prog...http/1.1
/sites/default/themes/custom/cernbase/css/components/acco...http/1.1
/sites/default/themes/custom/cernbase/css/components/soci...http/1.1
framework.web.cern.ch/framework/3.0/js/colorbox/colorbox.csshttp/1.1
home.cern/sites/default/themes/custom/cernbase/css/theme.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/cookies.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/viewspage.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/views/faq-views.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/views/agenda-views.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/views/news-views.css?tckkx1http/1.1
/sites/default/themes/custom/cernbase/css/views/stories-v...http/1.1
/sites/default/themes/custom/cernbase/css/views/resources...http/1.1
/sites/default/themes/custom/cernbase/css/views/taxonomie...http/1.1
home.cern/sites/default/themes/custom/cernbase/css/views/search-views.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/css/views/common-views.css?tckkx1http/1.1
/sites/default/themes/custom/cernbase/css/views/generic-v...http/1.1
home.cern/sites/default/themes/custom/cernpublic/css/layout.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernpublic/css/overrides.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernpublic/css/header.css?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernpublic/css/views.css?tckkx1http/1.1
framework.web.cern.ch/framework/3.0/images/loader.gifhttp/1.1
home.cern/sites/default/files/logo/cern-logo.pnghttp/1.1
home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.1http/1.1
home.cern/core/assets/vendor/underscore/underscore-min.js?v=1.13.7http/1.1
home.cern/core/assets/vendor/once/once.min.js?v=1.0.1http/1.1
/sites/default/files/languages/en_p5SjUX5jHQqdSjFPWYikWHz...http/1.1
home.cern/core/misc/drupalSettingsLoader.js?v=10.4.5http/1.1
home.cern/core/misc/drupal.js?v=10.4.5http/1.1
home.cern/core/misc/drupal.init.js?v=10.4.5http/1.1
home.cern/core/assets/vendor/tabbable/index.umd.min.js?v=6.2.0http/1.1
home.cern/core/misc/progress.js?v=10.4.5http/1.1
home.cern/themes/contrib/bootstrap/js/misc/progress.js?tckkx1http/1.1
home.cern/core/assets/vendor/loadjs/loadjs.min.js?v=4.3.0http/1.1
home.cern/core/misc/debounce.js?v=10.4.5http/1.1
home.cern/core/misc/announce.js?v=10.4.5http/1.1
home.cern/core/misc/message.js?v=10.4.5http/1.1
home.cern/themes/contrib/bootstrap/js/misc/message.js?tckkx1http/1.1
home.cern/core/misc/ajax.js?v=10.4.5http/1.1
home.cern/themes/contrib/bootstrap/js/misc/ajax.js?tckkx1http/1.1
/sites/default/themes/custom/cernbase/sass/bootstrap/java...http/1.1
home.cern/themes/contrib/bootstrap/js/drupal.bootstrap.js?tckkx1http/1.1
home.cern/themes/contrib/bootstrap/js/attributes.js?tckkx1http/1.1
home.cern/themes/contrib/bootstrap/js/theme.js?tckkx1http/1.1
home.cern/themes/contrib/bootstrap/js/popover.js?tckkx1http/1.1
home.cern/themes/contrib/bootstrap/js/tooltip.js?tckkx1http/1.1
home.cern/modules/custom/cern-loading/js/cern_loading.js?tckkx1http/1.1
home.cern/modules/custom/cern-toolbar/assets/js/cern_toolbar.js?v=1.xhttp/1.1
framework.web.cern.ch/framework/3.0/js/prism/prism.jshttp/1.1
home.cern/sites/default/themes/custom/cernbase/js/cernbase.js?tckkx1http/1.1
/sites/default/themes/custom/cernbase/js/components/socia...http/1.1
home.cern/sites/default/themes/custom/cernbase/js/components/footer.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/agenda-views.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/faq-views.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/news-views.js?tckkx1http/1.1
/sites/default/themes/custom/cernbase/js/views/resources-...http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/stories-views.js?tckkx1http/1.1
/sites/default/themes/custom/cernbase/js/views/taxonomies...http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/search-views.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/js/views/common-views.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernbase/js/box-effects.js?tckkx1http/1.1
framework.web.cern.ch/framework/3.0/js/colorbox/jquery.colorbox-min.jshttp/1.1
framework.web.cern.ch/framework/3.0/js/scroll-magic/ScrollMagic.min.jshttp/1.1
framework.web.cern.ch/framework/3.0/js/scroll-magic/text-effects.jshttp/1.1
framework.web.cern.ch/framework/3.0/js/owlcarousel/js/owl.carousel.jshttp/1.1
framework.web.cern.ch/framework/3.0/js/owlcarousel/js/owl.carousel2.thumbs.jshttp/1.1
home.cern/sites/default/themes/custom/cernpublic/js/views_carousel.js?tckkx1http/1.1
home.cern/sites/default/themes/custom/cernpublic/js/anchor-fix.js?tckkx1http/1.1
home.cern/sites/default/modules/mathjax/js/config.js?v=10.4.5http/1.1
home.cern/libraries/MathJax/MathJax.js?config=TeX-AMS-MML_HTMLorMMLhttp/1.1
home.cern/sites/default/modules/mathjax/js/setup.js?v=10.4.5http/1.1
home.cern/modules/contrib/matomo/js/matomo.js?v=10.4.5http/1.1
/modules/custom/cern-components/patterns/atoms/background...http/1.1
/modules/custom/cern-components/patterns/molecules/header...http/1.1
/modules/custom/cern-components/patterns/molecules/menu/j...http/1.1
/modules/custom/cern-components/patterns/molecules/previe...http/1.1
/modules/custom/cern-components/patterns/molecules/row/js...http/1.1
home.cern/modules/custom/cern-loading/images/loader.gifhttp/1.1
home.cern/modules/custom/cern-toolbar/assets/img/toolbarsprite.pnghttp/1.1
/sites/default/files/styles/large/public/2026-04/ATLAS_co...http/1.1
/sites/default/files/styles/large/public/2026-04/IMG_7455...http/1.1
/sites/default/files/styles/large/public/2026-04/collisio...http/1.1
/sites/default/files/styles/large/public/2026-03/Image_Ch...http/1.1
home.cern/sites/default/files/2026-04/55182696113-0c4398702d-o-2_0.jpghttp/1.1
/sites/default/files/styles/large/public/2026-04/Kart-144...http/1.1
/sites/default/files/styles/large/public/2026-03/Mosaic_s...http/1.1
/sites/default/files/styles/large/public/2026-03/Toponium...http/1.1
/sites/default/files/styles/large/public/2026-03/202603-0...http/1.1
home.cern/sites/default/files/2025-12/202310-230_50_2_1.jpghttp/1.1
home.cern/sites/default/files/2025-12/Screenshot-vitual-tour_1.jpghttp/1.1
/sites/default/files/2025-12/Artist Rasheedah Phillips fr...http/1.1
home.cern/sites/default/files/2025-12/OPEN-PHO-CIVIL-2023-001-6_0_1.jpeghttp/1.1
home.cern/sites/default/files/2025-12/CERN-EX-1212264-01_0_1.jpghttp/1.1
home.cern/sites/default/files/2025-12/ATLAS-PHO-EVENTS-2014-010-1_1.jpghttp/1.1
home.cern/sites/default/files/2025-12/CERN-AC-0911188-01_2.jpghttp/1.1
home.cern/sites/default/files/2025-12/CERN-EX-23296-1_1.jpghttp/1.1
home.cern/sites/default/files/2025-12/CERN-GE-9407011-31_1.jpghttp/1.1
home.cern/sites/default/files/2025-12/69576_1.jpeghttp/1.1
home.cern/sites/default/files/2025-12/60100_2.jpeghttp/1.1
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/regular.woff2http/1.1
framework.web.cern.ch/framework/3.0/fonts/open-sans/bold.woff2http/1.1
framework.web.cern.ch/framework/3.0/fonts/cern/cern.woff2http/1.1
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/semibold.woff2http/1.1
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/light.woff2http/1.1
framework.web.cern.ch/framework/3.0/fonts/sourcesanspro/bold.woff2http/1.1
home.cern/sites/default/files/2026-04/Toponium.pnghttp/1.1
home.cern/sites/default/files/2026-04/Antimatter-3.pnghttp/1.1
home.cern/sites/default/files/2026-04/ALICE.pnghttp/1.1
home.cern/sites/default/themes/custom/cernpublic/favicon.icohttp/1.1

Avoid chaining critical requests by reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load.

Why this matters

Performance issues directly impact user engagement and conversion rates.

description: [preconnect](https://developer.chrome.com/docs/lighthouse/performance/uses-rel-preconnect/) hints help the browser establish a connection earlier in the page load, saving time when the first request for that origin is made. The following are the origins that the page preconnected to.
title: Preconnected origins
value: no origins were preconnected
description: Add [preconnect](https://developer.chrome.com/docs/lighthouse/performance/uses-rel-preconnect/) hints to your most important origins, but try to use no more than 4.
title: Preconnect candidates

Requests are blocking the page's initial render, which may delay LCP. Deferring or inlining can move these network requests out of the critical path.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLTransfer SizeDuration
home.cern/core/assets/vendor/jquery/jquery.min.js?v=3.7.130.2 KiB1.4 s
home.cern/sites/default/themes/custom/cernpublic/css/views.css?tckkx11.1 KiB152 ms
home.cern/sites/default/themes/custom/cernpublic/css/blocks.css?tckkx10 B152 ms
home.cern/sites/default/themes/custom/cernpublic/css/header.css?tckkx1470 B152 ms
home.cern/sites/default/themes/custom/cernpublic/css/overrides.css?tckkx1688 B152 ms
home.cern/sites/default/themes/custom/cernpublic/css/layout.css?tckkx11.6 KiB152 ms
/sites/default/themes/custom/cernbase/css/views/generic-v...4.0 KiB302 ms
home.cern/sites/default/themes/custom/cernbase/css/views/common-views.css?tckkx1967 B152 ms
home.cern/sites/default/themes/custom/cernbase/css/views/search-views.css?tckkx11.6 KiB452 ms
/sites/default/themes/custom/cernbase/css/views/taxonomie...1.6 KiB452 ms
/sites/default/themes/custom/cernbase/css/views/resources...3.2 KiB602 ms
/sites/default/themes/custom/cernbase/css/views/stories-v...750 B452 ms
home.cern/sites/default/themes/custom/cernbase/css/views/news-views.css?tckkx13.2 KiB602 ms
home.cern/sites/default/themes/custom/cernbase/css/views/faq-views.css?tckkx11.8 KiB452 ms
home.cern/sites/default/themes/custom/cernbase/css/views/agenda-views.css?tckkx13.5 KiB602 ms
home.cern/sites/default/themes/custom/cernbase/css/viewspage.css?tckkx1477 B452 ms
home.cern/sites/default/themes/custom/cernbase/css/cookies.css?tckkx11008 B452 ms
home.cern/sites/default/themes/custom/cernbase/css/theme.css?tckkx15.6 KiB602 ms
/sites/default/themes/custom/cernbase/css/components/acco...860 B452 ms
/sites/default/themes/custom/cernbase/css/components/drop...1.6 KiB452 ms
/sites/default/themes/custom/cernbase/css/components/soci...946 B452 ms
/sites/default/themes/custom/cernbase/css/components/prog...1.0 KiB452 ms
home.cern/sites/default/themes/custom/cernbase/css/components/fields.css?tckkx1970 B452 ms
home.cern/sites/default/themes/custom/cernbase/css/components/forms.css?tckkx12.3 KiB452 ms
home.cern/sites/default/themes/custom/cernbase/css/components/header.css?tckkx13.2 KiB602 ms
/sites/default/themes/custom/cernbase/css/components/pagi...1.3 KiB452 ms
home.cern/sites/default/themes/custom/cernbase/css/layout.css?tckkx13.0 KiB602 ms
home.cern/sites/default/themes/custom/cernbase/css/components/footer.css?tckkx11.8 KiB452 ms
home.cern/sites/default/themes/custom/cernbase/css/base.css?tckkx123.1 KiB1.7 s
home.cern/sites/default/files/color/cernpublic-ac827e9a/colors.css?tckkx15.8 KiB752 ms
home.cern/modules/contrib/paragraphs/css/paragraphs.unpublished.css?tckkx1314 B452 ms
/modules/custom/cern-components/patterns/molecules/row/cs...2.3 KiB452 ms
home.cern/core/modules/layout_discovery/layouts/onecol/onecol.css?tckkx1374 B452 ms
home.cern/core/modules/views/css/views.module.css?tckkx1692 B452 ms
/modules/custom/cern-components/patterns/molecules/previe...2.8 KiB452 ms
/modules/custom/cern-components/patterns/molecules/menu/c...5.0 KiB602 ms
/modules/custom/cern-components/patterns/molecules/header...2.9 KiB602 ms
/modules/custom/cern-components/patterns/molecules/header...1.1 KiB452 ms
/modules/custom/cern-components/patterns/molecules/margin...438 B452 ms
/modules/custom/cern-components/patterns/atoms/background...844 B452 ms
/modules/custom/cern-components/patterns/molecules/agenda...2.6 KiB452 ms
framework.web.cern.ch/framework/3.0/js/owlcarousel/css/owl.carousel.css1.5 KiB756 ms
home.cern/modules/custom/cern-toolbar/assets/css/screen.css?tckkx12.0 KiB452 ms
/core/modules/system/css/components/system-status-report-...513 B452 ms
home.cern/core/modules/system/css/components/tablesort.module.css?tckkx1623 B452 ms
home.cern/modules/custom/cern-toolbar/assets/css/cookieconsent.css?tckkx1781 B452 ms
framework.web.cern.ch/framework/3.0/js/owlcarousel/css/owl.theme.default.css949 B756 ms
framework.web.cern.ch/framework/3.0/js/prism/prism.css2.3 KiB456 ms
framework.web.cern.ch/framework/3.0/js/colorbox/colorbox.css1.5 KiB456 ms
/core/modules/system/css/components/system-status-report-...815 B452 ms
home.cern/core/modules/system/css/components/system-status-counter.css?tckkx11023 B452 ms
home.cern/core/modules/system/css/components/resize.module.css?tckkx1528 B452 ms
/core/modules/system/css/components/position-container.mo...352 B452 ms
home.cern/core/modules/system/css/components/nowrap.module.css?tckkx1353 B452 ms
home.cern/core/modules/system/css/components/reset-appearance.module.css?tckkx1507 B452 ms
home.cern/core/modules/system/css/components/js.module.css?tckkx1920 B452 ms
home.cern/core/modules/system/css/components/item-list.module.css?tckkx1545 B452 ms
home.cern/core/modules/system/css/components/hidden.module.css?tckkx1955 B452 ms
home.cern/core/modules/system/css/components/fieldgroup.module.css?tckkx1352 B452 ms
home.cern/core/modules/system/css/components/details.module.css?tckkx1385 B452 ms
home.cern/core/modules/system/css/components/clearfix.module.css?tckkx1565 B452 ms
home.cern/core/modules/system/css/components/container-inline.module.css?tckkx1533 B452 ms
home.cern/core/modules/system/css/components/align.module.css?tckkx1742 B452 ms
home.cern/core/misc/components/progress.module.css?tckkx11.1 KiB452 ms
home.cern/modules/custom/cern-loading/css/cern_loading.css?tckkx1453 B152 ms

These insights are also available in the Chrome DevTools Performance Panel - record a trace to view more detailed information.

Time to Interactive is the amount of time it takes for the page to become fully interactive. Learn more about the Time to Interactive metric.

Why this matters

Performance issues directly impact user engagement and conversion rates.

TTI

Redirects introduce additional delays before the page can be loaded. Learn how to avoid page redirects.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 753 ms
URLTime Spent
cern.ch/753 ms
home.cern/0.0 ms

The maximum potential First Input Delay that your users could experience is the duration of the longest task. Learn more about the Maximum Potential First Input Delay metric.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Diagnostics

Minifying JavaScript files can reduce payload sizes and script parse time. Learn how to minify JavaScript.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 120 ms 26.9 KiB
URLTransfer SizeEst Savings
home.cern/core/misc/ajax.js?v=10.4.517.0 KiB11.9 KiB
framework.web.cern.ch/framework/3.0/js/owlcarousel/js/owl.carousel.js18.5 KiB7.2 KiB
home.cern/core/misc/drupal.js?v=10.4.56.1 KiB4.8 KiB
home.cern/themes/contrib/bootstrap/js/drupal.bootstrap.js?tckkx14.9 KiB2.9 KiB

Reduce unused rules from stylesheets and defer CSS not used for above-the-fold content to decrease bytes consumed by network activity. Learn how to reduce unused CSS.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 150 ms 22.1 KiB
URLTransfer SizeEst Savings
home.cern/sites/default/themes/custom/cernbase/css/base.css?tckkx122.8 KiB22.1 KiB

Consider reducing the time spent parsing, compiling and executing JS. You may find delivering smaller JS payloads helps with this. Learn how to minimize main-thread work

Why this matters

Performance issues directly impact user engagement and conversion rates.

CategoryTime Spent
Other965 ms
Script Evaluation762 ms
Style & Layout414 ms
Parse HTML & CSS138 ms
Script Parsing & Compilation83 ms
Rendering47 ms
Garbage Collection21 ms

Minifying CSS files can reduce network payload sizes. Learn how to minify CSS.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 0.0 ms 4.3 KiB
URLTransfer SizeEst Savings
home.cern/sites/default/themes/custom/cernbase/css/base.css?tckkx123.1 KiB4.3 KiB

Large network payloads cost users real money and are highly correlated with long load times. Learn how to reduce payload sizes.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URLTransfer Size
home.cern/sites/default/files/2026-04/ALICE.png6.1 MiB
home.cern/sites/default/files/2026-04/Antimatter-3.png5.0 MiB
home.cern/sites/default/files/2026-04/Toponium.png1.3 MiB
home.cern/sites/default/files/2025-12/202310-230_50_2_1.jpg1.1 MiB
home.cern/sites/default/files/2026-04/55182696113-0c4398702d-o-2_0.jpg677.0 KiB
framework.web.cern.ch/framework/3.0/images/loader.gif512.8 KiB
home.cern/modules/custom/cern-loading/images/loader.gif512.7 KiB
home.cern/sites/default/files/2025-12/69576_1.jpeg427.0 KiB
home.cern/sites/default/files/2025-12/60100_2.jpeg300.6 KiB
/sites/default/files/2025-12/Artist Rasheedah Phillips fr...264.0 KiB

Set an explicit width and height on image elements to reduce layout shifts and improve CLS. Learn how to set image dimensions

Why this matters

Performance issues directly impact user engagement and conversion rates.

URL
home div.site-info > div.site-info__logo > a > img
home.cern/sites/default/files/logo/cern-logo.png

More information about the performance of your application. These numbers don't directly affect the Performance score.

●Layout shift culprits
●Optimize DOM size
●LCP breakdown
●Optimize viewport for mobile
●Reduce unused JavaScript
●JavaScript execution time 0.7 s
●Avoid long main-thread tasks 4 long tasks found
●Avoid non-composited animations 1 animated element found
●Page didn't prevent back/forward cache restoration
●Network Requests
●Network Round Trip Times 30 ms
●Server Backend Latencies 30 ms
●Tasks
●Diagnostics
●Metrics
●Screenshot Thumbnails
●Final Screenshot
●Script Treemap Data
●Resources Summary
●Initial server response time was short Root document took 30 ms
●Avoid large layout shifts 1 layout shift found
○INP breakdown
○User Timing marks and measures
91

Accessibility

These checks highlight opportunities to improve the accessibility of your web app. Automatic detection can only detect a subset of issues and does not guarantee the accessibility of your web app, so manual testing is also encouraged.

Contrast

Low-contrast text is difficult or impossible for many users to read. Learn how to provide sufficient color contrast.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Copyright body.page-node-193099 > footer > div.copy-wrapper > a

These are opportunities to improve the legibility of your content.

Navigation

Properly ordered headings that do not skip levels convey the semantic structure of the page, making it easier to navigate and understand when using assistive technologies. Learn more about heading order.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
ATLAS acts as a cosmic-ray laboratory div.component-preview-cards__box_wrapper > div.component-preview-cards__box > div.preview-card__title > h3.standard-title
Plan your CERN visit div.component-preview-cards__box_wrapper > div.component-preview-cards__box > div.preview-card__title > h3
Surprises in Vacuum Decay or Bounces, Pseudo-Bounces and Antibounce... div.agenda-box-pattern > div.agenda-box-pattern__box-wrapper > div.agenda-box-link > h3
The Higgs boson div.component-preview-cards__box_wrapper > div.component-preview-cards__box > div.preview-card__title > h3

These are opportunities to improve keyboard navigation in your application.

Names and labels

Link text (and alternate text for images, when used as links) that is discernible, unique, and focusable improves the navigation experience for screen reader users. Learn how to make links accessible.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--2 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--2 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--3 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--3 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--4 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--4 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--5 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--5 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--6 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--6 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--7 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--7 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--8 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--8 > a.box-link
div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--9 > a.box-link div.carousel-cern-item > div.horizontal-boxes-row > div#preview-card--9 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--17 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--17 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--18 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--18 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--19 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--19 > a.box-link
div.component-row__row > div.component-row__column > div#preview-card--20 > a.box-link div.component-row__row > div.component-row__column > div#preview-card--20 > a.box-link
div.component-row__row > div.component-row__column > div#preview-card--21 > a.box-link div.component-row__row > div.component-row__column > div#preview-card--21 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--28 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--28 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--29 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--29 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--30 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--30 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--31 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--31 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--32 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--32 > a.box-link
div.component-row__column > div.box-effects-wrapper > div#preview-card--33 > a.box-link div.component-row__column > div.box-effects-wrapper > div#preview-card--33 > a.box-link

These are opportunities to improve the semantics of the controls in your application. This may enhance the experience for users of assistive technology, like a screen reader.

○Interactive controls are keyboard focusable
○Interactive elements indicate their purpose and state
○The page has a logical tab order
○Visual order on the page follows DOM order
○User focus is not accidentally trapped in a region
○The user's focus is directed to new content added to the page
○HTML5 landmark elements are used to improve navigation
○Offscreen content is hidden from assistive technology
○Custom controls have associated labels
○Custom controls have ARIA roles
●`[aria-*]` attributes match their roles
●`[aria-hidden="true"]` is not present on the document `<body>`
●`[role]`s have all required `[aria-*]` attributes
●`[role]` values are valid
●`[aria-*]` attributes have valid values
●`[aria-*]` attributes are valid and not misspelled
●Buttons have an accessible name
●Image elements have `[alt]` attributes
●`[user-scalable="no"]` is not used in the `<meta name="viewport">` element and the `[maximum-scale]` attribute is not less than 5.
●ARIA attributes are used as specified for the element's role
●`[aria-hidden="true"]` elements do not contain focusable descendents
●Elements use only permitted ARIA attributes
●Document has a `<title>` element
●`<html>` element has a `[lang]` attribute
●`<html>` element has a valid value for its `[lang]` attribute
●Links are distinguishable without relying on color.
●Lists contain only `<li>` elements and script supporting elements (`<script>` and `<template>`).
●List items (`<li>`) are contained within `<ul>`, `<ol>` or `<menu>` parent elements
●No element has a `[tabindex]` value greater than 0
●Touch targets have sufficient size and spacing.
●Document has a main landmark.
●Deprecated ARIA roles were not used
●Identical links have the same purpose.
○`[accesskey]` values are unique
○`button`, `link`, and `menuitem` elements have accessible names
○Elements with `role="dialog"` or `role="alertdialog"` have accessible names.
○ARIA input fields have accessible names
○ARIA `meter` elements have accessible names
○ARIA `progressbar` elements have accessible names
○Elements with an ARIA `[role]` that require children to contain a specific `[role]` have all required children.
○`[role]`s are contained by their required parent element
○Elements with the `role=text` attribute do not have focusable descendents.
○ARIA toggle fields have accessible names
○ARIA `tooltip` elements have accessible names
○ARIA `treeitem` elements have accessible names
○The page contains a heading, skip link, or landmark region
○`<dl>`'s contain only properly-ordered `<dt>` and `<dd>` groups, `<script>`, `<template>` or `<div>` elements.
○Definition list items are wrapped in `<dl>` elements
○ARIA IDs are unique
○No form fields have multiple labels
○`<frame>` or `<iframe>` elements have a title
○`<html>` element has an `[xml:lang]` attribute with the same base language as the `[lang]` attribute.
○Input buttons have discernible text.
○`<input type="image">` elements have `[alt]` text
○Form elements have associated labels
○The document does not use `<meta http-equiv="refresh">`
○`<object>` elements have alternate text
○Select elements have associated label elements.
○Skip links are focusable.
○Cells in a `<table>` element that use the `[headers]` attribute refer to table cells within the same table.
○`<th>` elements and elements with `[role="columnheader"/"rowheader"]` have data cells they describe.
○`[lang]` attributes have a valid value
○`<video>` elements contain a `<track>` element with `[kind="captions"]`
○Tables have different content in the summary attribute and `<caption>`.
○All heading elements contain content.
○Uses ARIA roles only on compatible elements
○Image elements do not have `[alt]` attributes that are redundant text.
○Elements with visible text labels have matching accessible names.
○Tables use `<caption>` instead of cells with the `[colspan]` attribute to indicate a caption.
○`<td>` elements in a large `<table>` have one or more table headers.
96

Best Practices

General

Errors logged to the console indicate unresolved problems. They can come from network request failures and other browser concerns. Learn more about this errors in console diagnostic audit

Why this matters

Performance issues directly impact user engagement and conversion rates.

SourceDescription
home.cern/libraries/MathJax/MathJax.js?config=TeX-AMS-MML_HTMLorMML
Failed to load resource: the server responded with a status of 404 (Not Found)
home.cern/
Refused to apply style from 'https://home.cern/sites/default/themes/custom/cernpublic/css/blocks.css?tckkx1' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled.
home.cern/
Refused to execute script from 'https://home.cern/libraries/MathJax/MathJax.js?config=TeX-AMS-MML_HTMLorMML' because its MIME type ('text/html') is not executable, and strict MIME type checking is enabled.
●Uses HTTPS
●Avoids deprecated APIs
●Avoids third-party cookies
●Allows users to paste into input fields
●Avoids requesting the geolocation permission on page load
●Avoids requesting the notification permission on page load
●Displays images with correct aspect ratio
●Serves images with appropriate resolution
●Page has the HTML doctype
●Properly defines charset
●No issues in the `Issues` panel in Chrome Devtools
●Ensure CSP is effective against XSS attacks
●Use a strong HSTS policy
●Ensure proper origin isolation with COOP
●Mitigate DOM-based XSS with Trusted Types
●Detected JavaScript libraries
●Page has valid source maps
○Redirects HTTP traffic to HTTPS
○Mitigate clickjacking with XFO or CSP
100

SEO

These checks ensure that your page is following basic search engine optimization advice. There are many additional factors Lighthouse does not score here that may affect your search ranking, including performance on Core Web Vitals. Learn more about Google Search Essentials.

○Structured data is valid
●Page isn’t blocked from indexing
●Document has a `<title>` element
●Document has a meta description
●Page has successful HTTP status code
●Links have descriptive text
●Links are crawlable
●robots.txt is valid
●Image elements have `[alt]` attributes
●Document has a valid `hreflang`
●Document has a valid `rel=canonical`

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