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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.

39

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
cdn.eso.org/images/banner1920/eso2603a.jpg0.0 ms608.2 KiB
cdn.eso.org/images/banner1920/eso2518a.jpg0.0 ms506.4 KiB
cdn.eso.org/images/small169/potw2616a.jpg0.0 ms346.6 KiB
cdn.eso.org/images/banner1920/_DSC7159-CC.jpg0.0 ms346.3 KiB
cdn.eso.org/images/banner1920/eso2521a.jpg0.0 ms341.3 KiB
cdn.eso.org/images/small169/annlang26005a-es-cl.jpg0.0 ms275.4 KiB
cdn.eso.org/images/banner1920/eso2605a.jpg0.0 ms236.2 KiB
cdn.eso.org/images/banner1920/eso2519a.jpg0.0 ms214.6 KiB
cdn.eso.org/images/banner1920/eso2517a.jpg0.0 ms195.2 KiB
cdn.eso.org/images/banner1920/eso2604a.jpg0.0 ms161.7 KiB
cdn.eso.org/images/banner1920/eso2601a.jpg0.0 ms128.4 KiB
cdn.eso.org/videos/small169/cs0027a.jpg0.0 ms94.7 KiB
cdn.eso.org/images/small169/potw2615a.jpg0.0 ms81.0 KiB
cdn.eso.org/images/banner1920/eso2520a.jpg0.0 ms64.6 KiB
cdn.eso.org/images/small169/annlang26004a-es-cl.jpg0.0 ms59.5 KiB
www.eso.org/mtmo/matomo.js3600.0 s66.3 KiB
www.eso.org/public/archives/static/frontpage/alma.jpg604800.0 s254.2 KiB
cdn.eso.org/images/thumb350x/eso50_obs_compo.jpg0.0 ms23.0 KiB
www.eso.org/public/archives/static/frontpage/vlt.jpg604800.0 s211.6 KiB
www.eso.org/public/archives/djp/js/main.bf52206884ae.js604800.0 s195.0 KiB
cdn.eso.org/images/thumb350x/2018_04_17_es_moon-venus_4-cc.jpg0.0 ms18.7 KiB
/public/archives/djp/font-awesome/webfonts/fa-solid-900.d...604800.0 s146.9 KiB
www.eso.org/public/archives/static/frontpage/lasilla.jpg604800.0 s138.7 KiB
www.eso.org/public/archives/static/frontpage/elt.jpg604800.0 s117.8 KiB
www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.png604800.0 s87.6 KiB
www.eso.org/public/archives/djp/css/main.01d86ad5297f.css604800.0 s77.7 KiB
/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-46...604800.0 s41.8 KiB
/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48...604800.0 s41.7 KiB
/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-48...604800.0 s41.2 KiB
www.eso.org/public/archives/djp/css/extras.d3e54451ebbb.css604800.0 s13.9 KiB
/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af...1.0 s637 B
www.eso.org/public/archives/djp/js/main_privacy.11c2900c4c46.js604800.0 s2.1 KiB

Layout shifts occur when elements move absent any user interaction. Investigate the causes of layout shifts, such as elements being added, removed, or their fonts changing as the page loads.

Why this matters

Performance issues directly impact user engagement and conversion rates.

headings: [map[key:node label:Element subItemsHeading:map[key:extra] valueType:node] map[granularity:0.001 key:score label:Layout shift score subItemsHeading:map[key:cause valueType:text] valueType:numeric]]
items: [map[node:map[type:text value:Total] score:0.911776] map[node:map[boundingRect:map[bottom:2482 height:1959 left:0 right:412 top:523 width:412] lhId:page-25-DIV nodeLabel:Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… path:1,HTML,1,BODY,2,DIV,3,DIV selector:body > div#content > div#body snippet:<div class="container" id="body"> type:node] score:0.577157] map[node:map[boundingRect:map[bottom:2482 height:1959 left:0 right:412 top:523 width:412] lhId:page-25-DIV nodeLabel:Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… path:1,HTML,1,BODY,2,DIV,3,DIV selector:body > div#content > div#body snippet:<div class="container" id="body"> type:node] score:0.210139 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:279 height:193 left:0 right:412 top:86 width:412] lhId:page-22-IMG nodeLabel:The PoET main telescope path:1,HTML,1,BODY,2,DIV,0,DIV,1,DIV,0,DIV,0,DIV,1,DIV,0,A,0,IMG selector:div.slick-track > div.slide > a > img snippet:<img draggable="false" alt="The PoET main telescope" class="" src="https://cdn.eso.org/images/banner1920/eso2605a.jpg"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:2482 height:1959 left:0 right:412 top:523 width:412] lhId:page-25-DIV nodeLabel:Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… path:1,HTML,1,BODY,2,DIV,3,DIV selector:body > div#content > div#body snippet:<div class="container" id="body"> type:node] score:0.106147 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:279 height:193 left:-412 right:0 top:86 width:412] lhId:page-35-IMG nodeLabel:Andreas Kaufer at Paranal path:1,HTML,1,BODY,2,DIV,0,DIV,1,DIV,0,DIV,0,DIV,0,DIV,0,A,0,IMG selector:div.slick-track > div.slide > a > img snippet:<img draggable="false" alt="Andreas Kaufer at Paranal" class="" src="https://cdn.eso.org/images/banner1920/eso2517a.jpg"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:2482 height:1959 left:0 right:412 top:523 width:412] lhId:page-25-DIV nodeLabel:Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… path:1,HTML,1,BODY,2,DIV,3,DIV selector:body > div#content > div#body snippet:<div class="container" id="body"> type:node] score:0.018159 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:279 height:193 left:412 right:824 top:86 width:412] lhId:page-11-IMG nodeLabel:VLT images of two planets forming around the young star WISPIT 2 path:1,HTML,1,BODY,2,DIV,0,DIV,1,DIV,0,DIV,0,DIV,2,DIV,0,A,0,IMG selector:div.slick-track > div.slide > a > img snippet:<img draggable="false" alt="VLT images of two planets forming around the young star WISPIT 2" class="" src="https://cdn.eso.org/images/banner1920/eso2604a.jpg"> type:node]]] type:subitems]] map[node:map[boundingRect:map[bottom:31 height:22 left:196 right:326 top:9 width:131] lhId:page-23-DIV nodeLabel:Science User Portal path:1,HTML,1,BODY,0,NAV,0,DIV,2,DIV selector:body > nav.navbar-general-wrapper > div.navbar-general > div.sections snippet:<div class="sections"> type:node] score:0.000174 subItems:map[items:[map[cause:Unsized image element extra:map[boundingRect:map[bottom:823 height:103 left:10 right:196 top:720 width:186] lhId:page-15-IMG nodeLabel:Inside the world's largest telescope: it's progressing fast! path:1,HTML,1,BODY,2,DIV,3,DIV,1,DIV,0,DIV,0,A,0,DIV,0,IMG selector:div.story-container > a > div.story-img-container > img.story-img snippet:<img class="story-img" src="https://cdn.eso.org/videos/small169/cs0027a.jpg" alt="Inside the world's largest telescope: it's progressing fast!"> type:node]] map[cause:Web font extra:map[type:url value:https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2]]] type:subitems]]]

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
/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48...345 ms
/public/archives/djp/font-awesome/webfonts/fa-solid-900.d...190 ms
/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-48...175 ms
/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-46...175 ms

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
Largest ALMA image ever shows the molecular gas in the centre of the Milky Way div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2603a.jpg607.0 KiB567.3 KiB
The RCW 94/95 nebulae in visible and infrared light div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2518a.jpg505.3 KiB465.6 KiB
Aiming at a cosmic tarantula div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/potw2616a.jpg345.7 KiB336.0 KiB
Cerro Paranal and the Milky Way above it div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/_DSC7159-CC.jpg345.4 KiB305.8 KiB
CTAO-South time-capsule monument unveiling div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2521a.jpg340.4 KiB300.8 KiB
El Presidente de la República Checa y el Ministro de Relaciones Exteriores de C… div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/annlang26005a-es-cl.jpg274.6 KiB264.9 KiB
In search of our Cosmic Origins div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/alma.jpg253.8 KiB238.9 KiB
The PoET main telescope div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2605a.jpg235.4 KiB202.2 KiB
The world’s most advanced visible-light astronomical observatory div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/vlt.jpg211.2 KiB196.3 KiB
Four lasers for the VLTI div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2519a.jpg213.9 KiB183.8 KiB
Andreas Kaufer at Paranal div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2517a.jpg194.5 KiB167.0 KiB
VLT images of two planets forming around the young star WISPIT 2 div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2604a.jpg161.1 KiB138.3 KiB
ESO’s first observatory div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/lasilla.jpg138.4 KiB123.5 KiB
VLT image of a dead star creating a shock wave as it moves through space div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2601a.jpg127.8 KiB109.8 KiB
The World’s Biggest Eye on the Sky div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/elt.jpg117.4 KiB102.5 KiB
Inside the world's largest telescope: it's progressing fast! div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/videos/small169/cs0027a.jpg94.1 KiB84.4 KiB
Taxi, please! div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/potw2615a.jpg80.4 KiB70.7 KiB
div.social-links-container > div.social-icons-container > a > div.sprites-mastodon_white div.social-links-container > div.social-icons-container > a > div.sprites-mastodon_white
www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.png87.2 KiB56.7 KiB
Artist’s impression of the initial shape of a supernova explosion div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2520a.jpg64.1 KiB55.0 KiB
Tour nocturno en Observatorio Paranal div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/annlang26004a-es-cl.jpg58.9 KiB49.2 KiB
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
cdn.eso.org/images/thumb350x/eso50_obs_compo.jpg22.5 KiB11.5 KiB
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
cdn.eso.org/images/thumb350x/2018_04_17_es_moon-venus_4-cc.jpg18.3 KiB7.3 KiB

Each subpart has specific improvement strategies. Ideally, most of the LCP time should be spent on loading the resources, not within delays.

Why this matters

Performance issues directly impact user engagement and conversion rates.

headings: [map[key:label label:Subpart valueType:text] map[key:duration label:Duration valueType:ms]]
items: [map[duration:1084.371 label:Time to first byte subpart:timeToFirstByte] map[duration:1378.941 label:Resource load delay subpart:resourceLoadDelay] map[duration:25.913 label:Resource load duration subpart:resourceLoadDuration] map[duration:69.436 label:Element render delay subpart:elementRenderDelay]]
lhId: page-22-IMG
nodeLabel: The PoET main telescope
path: 1,HTML,1,BODY,2,DIV,0,DIV,1,DIV,0,DIV,0,DIV,1,DIV,0,A,0,IMG
selector: div.slick-track > div.slide > a > img
snippet: <img draggable="false" alt="The PoET main telescope" class="" src="https://cdn.eso.org/images/banner1920/eso2605a.jpg">

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-22-IMG
nodeLabel: The PoET main telescope
path: 1,HTML,1,BODY,2,DIV,0,DIV,1,DIV,0,DIV,0,DIV,1,DIV,0,A,0,IMG
selector: div.slick-track > div.slide > a > img
snippet: <img draggable="false" alt="The PoET main telescope" class="" src="https://cdn.eso.org/images/banner1920/eso2605a.jpg">

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
www.eso.org/public/http/1.1
www.eso.org/public/archives/djp/css/main.01d86ad5297f.csshttp/1.1
www.eso.org/public/archives/static/frontpage/elt.jpghttp/1.1
www.eso.org/public/archives/static/frontpage/alma.jpghttp/1.1
www.eso.org/public/archives/static/frontpage/vlt.jpghttp/1.1
www.eso.org/public/archives/static/frontpage/lasilla.jpghttp/1.1
www.eso.org/public/archives/djp/css/extras.d3e54451ebbb.csshttp/1.1
www.eso.org/public/archives/djp/js/main.bf52206884ae.jshttp/1.1
www.eso.org/public/archives/djp/js/main_privacy.11c2900c4c46.jshttp/1.1
www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.pnghttp/1.1
/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48...http/1.1
/public/archives/djp/font-awesome/webfonts/fa-solid-900.d...http/1.1
/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-48...http/1.1
/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-46...http/1.1
www.eso.org/mtmo/matomo.jshttp/1.1
www.eso.org/public/archives/favicon.icohttp/1.1
/mtmo/matomo.php?action_name=ESO&idsite=1&rec=1&r=187399&...http/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
value: No additional origins are good candidates for preconnecting

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
www.eso.org/public/archives/djp/css/main.01d86ad5297f.css77.7 KiB977 ms
/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af...637 B784 ms

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

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: 1.3 s
URLTime Spent
eso.org/1.3 s
www.eso.org/public/0.0 ms

These are the largest layout shifts observed on the page. Each table item represents a single layout shift, and shows the element that shifted the most. Below each item are possible root causes that led to the layout shift. Some of these layout shifts may not be included in the CLS metric value due to windowing. Learn how to improve CLS

Why this matters

Performance issues directly impact user engagement and conversion rates.

ElementLayout shift score
Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… body > div#content > div#body
0.577
Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… body > div#content > div#body
0.210
Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… body > div#content > div#body
0.106
Our Stories All Press Releases Announcements Pictures of the Week Blog Posts Vi… body > div#content > div#body
0.018
Science User Portal body > nav.navbar-general-wrapper > div.navbar-general > div.sections
0.000

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

Diagnostics

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: 450 ms 84.1 KiB
URLTransfer SizeEst Savings
www.eso.org/public/archives/djp/css/main.01d86ad5297f.css77.4 KiB70.9 KiB
www.eso.org/public/archives/djp/css/extras.d3e54451ebbb.css13.5 KiB13.2 KiB

Reduce unused JavaScript and defer loading scripts until they are required to decrease bytes consumed by network activity. Learn how to reduce unused JavaScript.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Estimated savings: 900 ms 184.5 KiB
URLTransfer SizeEst Savings
www.eso.org/public/archives/djp/js/main.bf52206884ae.js194.6 KiB146.0 KiB
www.eso.org/mtmo/matomo.js65.9 KiB38.5 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
Style & Layout895 ms
Other801 ms
Script Evaluation377 ms
Rendering227 ms
Script Parsing & Compilation119 ms
Parse HTML & CSS90 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 12.8 KiB
URLTransfer SizeEst Savings
www.eso.org/public/archives/djp/css/main.01d86ad5297f.css77.7 KiB12.8 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
cdn.eso.org/images/banner1920/eso2603a.jpg608.2 KiB
cdn.eso.org/images/banner1920/eso2518a.jpg506.4 KiB
cdn.eso.org/images/small169/potw2616a.jpg346.6 KiB
cdn.eso.org/images/banner1920/_DSC7159-CC.jpg346.3 KiB
cdn.eso.org/images/banner1920/eso2521a.jpg341.3 KiB
cdn.eso.org/images/small169/annlang26005a-es-cl.jpg275.4 KiB
www.eso.org/public/archives/static/frontpage/alma.jpg254.2 KiB
cdn.eso.org/images/banner1920/eso2605a.jpg236.2 KiB
cdn.eso.org/images/banner1920/eso2519a.jpg214.6 KiB
www.eso.org/public/archives/static/frontpage/vlt.jpg211.6 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
Andreas Kaufer at Paranal div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2517a.jpg
The PoET main telescope div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2605a.jpg
VLT images of two planets forming around the young star WISPIT 2 div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2604a.jpg
Largest ALMA image ever shows the molecular gas in the centre of the Milky Way div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2603a.jpg
Cerro Paranal and the Milky Way above it div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/_DSC7159-CC.jpg
VLT image of a dead star creating a shock wave as it moves through space div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2601a.jpg
CTAO-South time-capsule monument unveiling div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2521a.jpg
Artist’s impression of the initial shape of a supernova explosion div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2520a.jpg
Four lasers for the VLTI div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2519a.jpg
The RCW 94/95 nebulae in visible and infrared light div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2518a.jpg
Andreas Kaufer at Paranal div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2517a.jpg
The PoET main telescope div.slick-track > div.slide > a > img
cdn.eso.org/images/banner1920/eso2605a.jpg
Inside the world's largest telescope: it's progressing fast! div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/videos/small169/cs0027a.jpg
El Presidente de la República Checa y el Ministro de Relaciones Exteriores de C… div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/annlang26005a-es-cl.jpg
Aiming at a cosmic tarantula div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/potw2616a.jpg
Taxi, please! div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/potw2615a.jpg
Tour nocturno en Observatorio Paranal div.story-container > a > div.story-img-container > img.story-img
cdn.eso.org/images/small169/annlang26004a-es-cl.jpg
The World’s Biggest Eye on the Sky div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/elt.jpg
In search of our Cosmic Origins div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/alma.jpg
The world’s most advanced visible-light astronomical observatory div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/vlt.jpg
ESO’s first observatory div.slogan > a > div.img-wrapper > img.img-responsive
www.eso.org/public/archives/static/frontpage/lasilla.jpg
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
cdn.eso.org/images/thumb350x/2018_04_17_es_moon-venus_4-cc.jpg
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
cdn.eso.org/images/thumb350x/eso50_obs_compo.jpg

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

●Max Potential First Input Delay 110 ms
●Optimize DOM size
●Forced reflow
●Optimize viewport for mobile
●Minify JavaScript
●JavaScript execution time 0.4 s
●Avoid long main-thread tasks 9 long tasks found
●Page didn't prevent back/forward cache restoration
●Network Requests
●Network Round Trip Times 170 ms
●Server Backend Latencies 160 ms
●Tasks
●Diagnostics
●Metrics
●Screenshot Thumbnails
●Final Screenshot
●Script Treemap Data
●Resources Summary
●Initial server response time was short Root document took 180 ms
○INP breakdown
○User Timing marks and measures
○Avoid non-composited animations
71

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.

ARIA

Focusable descendents within an `[aria-hidden="true"]` element prevent those interactive elements from being available to users of assistive technologies like screen readers. Learn how `aria-hidden` affects focusable elements.

Why this matters

Informational: a Permissions-Policy directive showing feature -> allowed origins.

Source: MDN Permissions-Policy

Failing Elements
ESO2517 — PRESS RELEASE Andreas Kaufer appointed as next ESO Director General T… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2604 — PRESS RELEASE A Solar System in the making? Two planets spotted formi… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2603 — PRESS RELEASE Largest image of its kind shows hidden chemistry at the… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2602 — PRESS RELEASE AES Andes announces cancellation of INNA, the industria… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2601 — PRESS RELEASE Astronomers surprised by mysterious shock wave around d… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2521 — PRESS RELEASE Construction begins on the first and largest gamma-ray … div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2520 — PRESS RELEASE Unique shape of star’s explosion revealed just a day af… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2519 — PRESS RELEASE Laser trial run kickstarts new era of interferometry La… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2518 — PRESS RELEASE New image captures spooky bat signal in the sky A spook… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2517 — PRESS RELEASE Andreas Kaufer appointed as next ESO Director General T… div#pr-carousel > div.slick-list > div.slick-track > div.slide
ESO2605 — PRESS RELEASE First light for PoET: shining (sun)light on exoplanet r… div#pr-carousel > div.slick-list > div.slick-track > div.slide

These are opportunities to improve the usage of ARIA in your application which may enhance the experience for users of assistive technology, like a screen reader.

Names and labels

When a button doesn't have an accessible name, screen readers announce it as "button", making it unusable for users who rely on screen readers. Learn how to make buttons more accessible.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
nav.navbar-general-wrapper > div.navbar-general > div.searchbox > button#searchbox-button nav.navbar-general-wrapper > div.navbar-general > div.searchbox > button#searchbox-button
div.form-group > div.input-group > span.input-group-btn > button.btn div.form-group > div.input-group > span.input-group-btn > button.btn
div#content > div#pr-carousel-wrapper > div#pr-carousel > button.slide-prev div#content > div#pr-carousel-wrapper > div#pr-carousel > button.slide-prev
div#content > div#pr-carousel-wrapper > div#pr-carousel > button.slide-next div#content > div#pr-carousel-wrapper > div#pr-carousel > button.slide-next

Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more about the `alt` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img

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.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div.visitus-container > div.social-links-container > div.social-icons-container > a div.visitus-container > div.social-links-container > div.social-icons-container > a
div#content > div.privacy-settings > ul.ul-privacy > a div#content > div.privacy-settings > ul.ul-privacy > a
div.privacy-settings > ul.ul-privacy > li > a div.privacy-settings > ul.ul-privacy > li > a

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.

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
Press Releases div#body > div.title-categories > div.story-categories > span.story-category
Announcements div#body > div.title-categories > div.story-categories > span.story-category
Pictures of the Week div#body > div.title-categories > div.story-categories > span.story-category
Blog Posts div#body > div.title-categories > div.story-categories > span.story-category
Videos div#body > div.title-categories > div.story-categories > span.story-category
13 Mar 2026 — cs0027a div.story-container > a > div.story-description > div.date
20 Apr 2026 — annlang26005-es-cl-en div.story-container > a > div.story-description > div.date
20 Apr 2026 — potw2616 div.story-container > a > div.story-description > div.date
13 Apr 2026 — potw2615 div.story-container > a > div.story-description > div.date
10 Apr 2026 — annlang26004-es-cl-en div.story-container > a > div.story-description > div.date
More... div.stories-container > div.story-container > div.story-more-container > span.story-more
Send us your comments! div#content > div.footernote > div > a
Subscribe to receive news from ESO in your language div#content > div.footernote > div > a
Accelerated by CDN77 div#content > div.footernote > div > a
Terms & Conditions div#content > div.footernote > div > a
Cookie Settings and Policy div#content > div.footernote > div > span.footer-privacy-settings-link
OFF div.cookies-table-row-choice > div.cookies-table-cell > div.privacy-setting-toggle > span.privacy-option
OFF div.cookies-table-row-choice > div.cookies-table-cell > div.privacy-setting-toggle > span.privacy-option
OFF div#content > div.privacy-settings > div.privacy-setting-toggle > span.privacy-option

These are opportunities to improve the legibility of your content.

Tables and lists

Screen readers have a specific way of announcing lists. Ensuring proper list structure aids screen reader output. Learn more about proper list structure.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Brave Chrome Edge Firefox Safari body > div#content > div.privacy-settings > ul.ul-privacy

These are opportunities to improve the experience of reading tabular or list data using assistive technology, like a screen reader.

Best practices

Touch targets with sufficient size and spacing help users who may have difficulty targeting small controls to activate the targets. Learn more about touch targets.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Brave div.privacy-settings > ul.ul-privacy > li > a
Chrome div.privacy-settings > ul.ul-privacy > li > a
Edge div.privacy-settings > ul.ul-privacy > li > a
Firefox div.privacy-settings > ul.ul-privacy > li > a
Safari div.privacy-settings > ul.ul-privacy > li > a

One main landmark helps screen reader users navigate a web page. Learn more about landmarks.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
html html

These items highlight common accessibility best practices.

○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
●Form elements have associated labels
●`[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
●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.
●List items (`<li>`) are contained within `<ul>`, `<ol>` or `<menu>` parent elements
●No element has a `[tabindex]` value greater than 0
●Heading elements appear in a sequentially-descending order
●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
○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.
100

Best Practices

General

Source maps translate minified code to the original source code. This helps developers debug in production. In addition, Lighthouse is able to provide further insights. Consider deploying source maps to take advantage of these benefits. Learn more about source maps.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URL
www.eso.org/public/archives/djp/js/main.bf52206884ae.js
●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 browser errors logged to the console
●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 clickjacking with XFO or CSP
●Mitigate DOM-based XSS with Trusted Types
●Detected JavaScript libraries
○Redirects HTTP traffic to HTTPS
83

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.

Content Best Practices

Descriptive link text helps search engines understand your content. Learn how to make links more accessible.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Link destinationLink Text
www.eso.org/public/shopinfo/Information

Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more about the `alt` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img
div.visituss-container > a > div.visitus-container > img div.visituss-container > a > div.visitus-container > img

Format your HTML in a way that enables crawlers to better understand your app’s content.

○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 are crawlable
●robots.txt is valid
●Document has a valid `hreflang`
○Document has a valid `rel=canonical`

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