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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.

34

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
/binaries/content/gallery/ul2/headers/260422-header-front...0.0 ms591.4 KiB
www.universiteitleiden.nl/design-1.0/css/ul2external/screen.css?v=1.223.000.0 ms84.2 KiB
/binaries/content/gallery/ul2/headers/260422-header-front...0.0 ms76.7 KiB
/binaries/content/gallery/ul2/main-images/general/spotlig...0.0 ms61.3 KiB
/binaries/content/gallery/ul2/spotlight-fotos/220905_spot...0.0 ms52.9 KiB
/design-1.0/assets/fonts/vestulapro/vestulapro-semibold.w...0.0 ms42.8 KiB
/design-1.0/assets/fonts/vestulapro/vestulapro-regular.woff20.0 ms42.4 KiB
www.universiteitleiden.nl/design-1.0/scripts/lib/jquery.js?v=1.223.000.0 ms32.0 KiB
www.universiteitleiden.nl/design-1.0/assets/images/world-map.png0.0 ms29.3 KiB
www.universiteitleiden.nl/design-1.0/assets/fonts/fontello/fontello.woff20.0 ms26.3 KiB
/binaries/content/gallery/ul2student/governance-and-globa...0.0 ms7.0 KiB
www.universiteitleiden.nl/design-1.0/assets/images/zegel.png0.0 ms6.6 KiB
/binaries/content/gallery/ul2/banners/banner-covid-boek-b...0.0 ms4.8 KiB
/binaries/content/gallery/ul2/main-images/law/publiekrech...0.0 ms4.4 KiB
/design-1.0/scripts/ul2common/mobile-fit-menu-items.js?v=...0.0 ms2.6 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/suggest.js?v=1.223.000.0 ms2.0 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/main.js0.0 ms1.8 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/ajax.js?v=1.223.000.0 ms1.6 KiB
/design-1.0/scripts/ul2common/nav-disclosure.js?v=1.223.000.0 ms1.6 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/search.js?v=1.223.000.0 ms1.5 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2.js?v=1.223.000.0 ms1.3 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/bgset.js?v=1.223.000.0 ms1.3 KiB
/design-1.0/scripts/ul2common/nav-hamburger.js?v=1.223.000.0 ms1.2 KiB
www.universiteitleiden.nl/design-1.0/scripts/ul2common/track-event.js?v=1.223.000.0 ms1.0 KiB
/design-1.0/scripts/ul2common/trigger-click.js?v=1.223.000.0 ms1016 B
www.universiteitleiden.nl/design-1.0/scripts/ul2common/box-more.js?v=1.223.000.0 ms902 B

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:0.312446] map[node:map[boundingRect:map[bottom:2219 height:1847 left:0 right:412 top:372 width:412] lhId:page-5-DIV nodeLabel:Kies een studie Maak een keuze uit het brede aanbod van: Bacheloropleidingen … path:1,HTML,1,BODY,5,DIV,0,DIV,1,DIV selector:body.full > div.main-container > div.main > div#content snippet:<div id="content"> type:node] score:0.312446]]

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
www.universiteitleiden.nl/design-1.0/assets/fonts/fontello/fontello.woff275 ms
/design-1.0/assets/fonts/vestulapro/vestulapro-semibold.w...65 ms
/design-1.0/assets/fonts/vestulapro/vestulapro-regular.woff235 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
body.full > div.home-hero > img body.full > div.home-hero > img
/binaries/content/gallery/ul2/headers/260422-header-front...590.8 KiB560.3 KiB
Hoe meet je vooruitgang?  body.full > div.home-hero
/binaries/content/gallery/ul2/headers/260422-header-front...75.9 KiB62.4 KiB
div.box-content > a > figure > img div.box-content > a > figure > img
/binaries/content/gallery/ul2/main-images/general/spotlig...69.0 KiB52.3 KiB
div.box-content > a > figure > img div.box-content > a > figure > img
/binaries/content/gallery/ul2/spotlight-fotos/220905_spot...52.1 KiB43.2 KiB
ul > li > a > img ul > li > a > img
/binaries/content/gallery/ul2student/governance-and-globa...7.4 KiB6.6 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-1-DIV
nodeLabel: Hoe meet je vooruitgang? 
path: 1,HTML,1,BODY,4,DIV
selector: body.full > div.home-hero
snippet: <div class="home-hero right " style="background-image: url(&quot;/binaries/content/gallery/ul2/headers/260422-header…&quot;);">

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.universiteitleiden.nl/http/1.1
www.universiteitleiden.nl/design-1.0/css/ul2external/screen.css?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/assets/images/zegel.pnghttp/1.1
/binaries/content/gallery/ul2/headers/260422-header-front...http/1.1
/binaries/content/gallery/ul2/main-images/law/publiekrech...http/1.1
/binaries/content/gallery/ul2student/governance-and-globa...http/1.1
/binaries/content/gallery/ul2/banners/banner-covid-boek-b...http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/assets/images/world-map.pnghttp/1.1
/design-1.0/assets/fonts/vestulapro/vestulapro-regular.woff2http/1.1
/design-1.0/assets/fonts/vestulapro/vestulapro-semibold.w...http/1.1
www.universiteitleiden.nl/design-1.0/assets/fonts/fontello/fontello.woff2http/1.1
www.universiteitleiden.nl/design-1.0/scripts/lib/jquery.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/main.jshttp/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/ajax.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/bgset.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/box-more.js?v=1.223.00http/1.1
/design-1.0/scripts/ul2common/mobile-fit-menu-items.js?v=...http/1.1
/design-1.0/scripts/ul2common/nav-hamburger.js?v=1.223.00http/1.1
/design-1.0/scripts/ul2common/nav-disclosure.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/search.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/suggest.js?v=1.223.00http/1.1
www.universiteitleiden.nl/design-1.0/scripts/ul2common/track-event.js?v=1.223.00http/1.1
/design-1.0/scripts/ul2common/trigger-click.js?v=1.223.00http/1.1
/async/spotlightcarousel?uuid=41c6a7b1-d88f-4337-ada5-f30...http/1.1
/async/spotlightcarousel?uuid=fc5cde43-ac54-4064-8dfe-d3a...http/1.1
/binaries/content/gallery/ul2/headers/260422-header-front...http/1.1
/binaries/content/gallery/ul2/spotlight-fotos/220905_spot...http/1.1
/binaries/content/gallery/ul2/main-images/general/spotlig...http/1.1
www.universiteitleiden.nl/design-1.0/assets/icons/favicon.icohttp/1.1
www.universiteitleiden.nl/design-1.0/assets/icons/icon-32px.pnghttp/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
www.universiteitleiden.nl/design-1.0/css/ul2external/screen.css?v=1.223.0084.2 KiB622 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: 805 ms
URLTime Spent
universiteitleiden.nl/805 ms
www.universiteitleiden.nl/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
Kies een studie Maak een keuze uit het brede aanbod van: Bacheloropleidingen … body.full > div.main-container > div.main > div#content
0.312

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

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 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: 160 ms 31.7 KiB
URLTransfer SizeEst Savings
www.universiteitleiden.nl/design-1.0/css/ul2external/screen.css?v=1.223.0084.2 KiB31.7 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: 640 ms 79.5 KiB
URLTransfer SizeEst Savings
www.universiteitleiden.nl/design-1.0/css/ul2external/screen.css?v=1.223.0083.5 KiB79.5 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: 1.0 s 238.7 KiB
URLTransfer SizeEst Savings
www.googletagmanager.com/gtm.js?id=GTM-P7SF446176.1 KiB70.0 KiB
www.googletagmanager.com/gtag/js?id=G-0RSX4L0ZPZ&cx=c&gtm=4e64k0172.9 KiB65.3 KiB
www.googletagmanager.com/gtag/js?id=G-CRX4PM593G&cx=c&gtm=4e64k0156.8 KiB63.7 KiB
chromewebdata/55.4 KiB39.7 KiB

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: 0.0 ms 21.8 KiB
URLTransfer SizeEst Savings
inline: // Copyright 2022 The Chromium Authors …55.4 KiB21.8 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
body.full > div.home-hero > img body.full > div.home-hero > img
/binaries/content/gallery/ul2/headers/260422-header-front...
div.box-content > a > figure > img div.box-content > a > figure > img
/binaries/content/gallery/ul2/spotlight-fotos/220905_spot...
div.box-content > a > figure > img div.box-content > a > figure > img
/binaries/content/gallery/ul2/main-images/general/spotlig...

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

●Optimize DOM size
●Forced reflow
●LCP breakdown
●Optimize viewport for mobile
●Avoids enormous network payloads Total size was 1,602 KiB
●User Timing marks and measures 10 user timings
●JavaScript execution time 1.0 s
●Minimizes main-thread work 1.7 s
●Avoid long main-thread tasks 6 long tasks found
●Page didn't prevent back/forward cache restoration
●Network Requests
●Network Round Trip Times 30 ms
●Server Backend Latencies 10 ms
●Tasks
●Diagnostics
●Metrics
●Screenshot Thumbnails
●Final Screenshot
●Script Treemap Data
●Resources Summary
●Initial server response time was short Root document took 40 ms
○INP breakdown
○Avoid non-composited animations
89

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
Bacheloropleidingen section > ul > li > a
Masteropleidingen section > ul > li > a
Opleidingen voor professionals section > ul > li > a
Bachelor voorlichtingsactiviteiten section > ul > li > a
Master voorlichtingsactiviteiten section > ul > li > a
Chat met een bachelorstudent section > ul > li > a
Chat met een masterstudent section > ul > li > a
Studievoorlichting li > a > div > span.meta
Studievoorlichting li > a > div > span.meta
Deze website maakt gebruik van cookies.  Meer informatie. Cookies accepteren Co… body.full > div.cookies > div.wrapper
Meer informatie. body.full > div.cookies > div.wrapper > a
Cookies weigeren div.cookies > div.wrapper > form > button.reject

These are opportunities to improve the legibility of your content.

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
Bacheloropleidingen section > ul > li > a
Masteropleidingen section > ul > li > a
Opleidingen voor professionals section > ul > li > a
Bachelor voorlichtingsactiviteiten section > ul > li > a
Master voorlichtingsactiviteiten section > ul > li > a
Chat met een bachelorstudent section > ul > li > a
Chat met een masterstudent section > ul > 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>`
●`[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
●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.
●Links have a discernible name
●Lists contain only `<li>` elements and script supporting elements (`<script>` and `<template>`).
●List items (`<li>`) are contained within `<ul>`, `<ol>` or `<menu>` parent elements
●Heading elements appear in a sequentially-descending order
○`[accesskey]` values are unique
○`button`, `link`, and `menuitem` elements have accessible names
○Deprecated ARIA roles were not used
○Elements with `role="dialog"` or `role="alertdialog"` have accessible names.
○`[aria-hidden="true"]` elements do not contain focusable descendents
○ARIA input fields have accessible names
○ARIA `meter` elements have accessible names
○ARIA `progressbar` elements have accessible names
○`[role]`s have all required `[aria-*]` attributes
○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
○`[role]` values are valid
○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.
○No element has a `[tabindex]` value greater than 0
○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.
○Identical links have the same purpose.
○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
chromewebdata/
Refused to display 'https://gtm.universiteitleiden.nl/' in a frame because it set 'X-Frame-Options' to 'sameorigin'.
●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
●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
○Use a strong HSTS policy
○Mitigate clickjacking with XFO or CSP
92

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.

Crawling and Indexing

If your robots.txt file is malformed, crawlers may not be able to understand how you want your website to be crawled or indexed. Learn more about robots.txt.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Line #ContentError
3<pre>Syntax not understood
10</pre>Syntax not understood

To appear in search results, crawlers need access to your app.

○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
●Image elements have `[alt]` attributes
●Document has a valid `hreflang`
●Document has a valid `rel=canonical`

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