Lighthouse Mobile

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

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Detailed Report

Audit breakdown by category with detailed findings.

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.

Request	Cache TTL	Transfer Size
royalsociety.org/assets/js/main.js	0.0 ms	54.1 KiB
cdn-ukwest.onetrust.com/scripttemplates/202401.2.0/otBannerSdk.js	86400.0 s	104.5 KiB
royalsociety.org/assets/css/main.css	0.0 ms	24.9 KiB
royalsociety.org/assets/images/logo@2x.png	0.0 ms	9.9 KiB
cdn-ukwest.onetrust.com/logos/static/ot_company_logo.png	86400.0 s	19.2 KiB
royalsociety.org/assets/js/799.c9cdc01946610cfc5be8.js	0.0 ms	5.0 KiB
royalsociety.org/assets/js/803.a16ce658ac8316e1725f.js	0.0 ms	4.2 KiB
cdn-ukwest.onetrust.com/scripttemplates/otSDKStub.js	86400.0 s	9.1 KiB
royalsociety.org/assets/js/328.4e865f0ff4b6617398bf.js	0.0 ms	3.3 KiB
royalsociety.org/assets/webfonts/fa-regular-400.woff2	0.0 ms	3.3 KiB
royalsociety.org/assets/webfonts/fa-brands-400.woff2	0.0 ms	2.8 KiB
royalsociety.org/assets/js/456.125a0f608fef09c28dcb.js	0.0 ms	2.5 KiB
royalsociety.org/assets/js/313.315b622b684d018b1cdf.js	0.0 ms	2.4 KiB
royalsociety.org/assets/webfonts/fa-solid-900.woff2	0.0 ms	2.3 KiB
royalsociety.org/assets/js/374.d9906402510d7122eae4.js	0.0 ms	2.1 KiB
cdn-ukwest.onetrust.com/logos/static/powered_by_logo.svg	86400.0 s	2.6 KiB
royalsociety.org/assets/css/custom.css	0.0 ms	948 B
/p.css?s=1&k=onn5raf&ht=tk&f=139.140.173.174.175.176&a=92...	604800.0 s	172 B

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.

URL	Est Savings
royalsociety.org/assets/webfonts/fa-regular-400.woff2	135 ms
royalsociety.org/assets/webfonts/fa-solid-900.woff2	110 ms
royalsociety.org/assets/webfonts/fa-brands-400.woff2	110 ms
/af/efe4a5/00000000000000007735e609/30/l?primer=7cdcb44be...	5.0 ms
/af/2555e1/00000000000000007735e603/30/l?primer=7cdcb44be...	5.0 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:Source valueType:source-location] map[granularity:1 key:reflowTime label:Total reflow time valueType:ms]]

items: [map[reflowTime:35.738 source:map[column:24738 line:1 type:source-location url:https://royalsociety.org/assets/js/main.js 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.

	URL	Resource Size	Est Savings
Welcome to the Royal Society We are the independent scientific academy of the … `body.sb-show-main > div.wrapper > main.main > div.hero`	/-/media/current-topics/des8801_website-transformation-pr...	660.5 KiB	473.0 KiB
The Royal Society `div.footer__info > div.footer__intro > div.footer__logo > img`	royalsociety.org/url(/-/media/navigation/footer/logoalt2x.png);	41.3 KiB	27.3 KiB
Dr Betina Ip, Professor Tamsin Mather FRS, Mike Barfield, Ben Shires, Helen Coo… `div.hero-card > a.hero-card__link > div.hero-card__figure > img.u-image-focal-point`	/-/media/science-book-prize/ypbp/2025/winner-2025-ypbp-ce...	56.5 KiB	21.4 KiB
The Royal Society `header.header > div.header__inner > a.header__logo > img.header__image`	royalsociety.org/assets/images/logo@2x.png	9.3 KiB	4.4 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-2-IMG

nodeLabel: Dr Betina Ip, Professor Tamsin Mather FRS, Mike Barfield, Ben Shires, Helen Coo…

path: 1,HTML,1,BODY,6,DIV,8,MAIN,0,DIV,0,DIV,2,DIV,0,DIV,0,A,0,DIV,0,IMG

selector: div.hero-card > a.hero-card__link > div.hero-card__figure > img.u-image-focal-point

snippet: <img class="u-image-focal-point hero-card__image" src="/-/media/science-book-prize/ypbp/2025/winner-2025-ypbp-ceremony.jpg" alt="Dr Betina Ip, Professor Tamsin Mather FRS, Mike Barfield, Ben Shires, Hele…">

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.

URL	Transfer Size	Duration
use.typekit.net/onn5raf.css	1.0 KiB	753 ms
/p.css?s=1&k=onn5raf&ht=tk&f=139.140.173.174.175.176&a=92...	172 B	789 ms
royalsociety.org/assets/css/main.css	24.9 KiB	173 ms
royalsociety.org/assets/css/custom.css	948 B

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.

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

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: 170 ms 37.7 KiB

URL	Transfer Size	Est Savings
royalsociety.org/assets/css/main.css	24.4 KiB	19.6 KiB
#onetrust-banner-sdk{-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%} …	20.4 KiB	18.1 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: 690 ms 164.8 KiB

URL	Transfer Size	Est Savings
www.googletagmanager.com/gtm.js?id=GTM-NS67FDG	168.9 KiB	83.8 KiB
cdn-ukwest.onetrust.com/scripttemplates/202401.2.0/otBannerSdk.js	104.3 KiB	54.6 KiB
royalsociety.org/assets/js/main.js	53.5 KiB	26.4 KiB

Many navigations are performed by going back to a previous page, or forwards again. The back/forward cache (bfcache) can speed up these return navigations. Learn more about the bfcache

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failure reason	Failure type
Pages with cache-control:no-store header cannot enter back/forward cache.	Actionable

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
The Royal Society `div.footer__info > div.footer__intro > div.footer__logo > img`	royalsociety.org/url(/-/media/navigation/footer/logoalt2x.png);
The Royal Society `header.header > div.header__inner > a.header__logo > img.header__image`	royalsociety.org/assets/images/logo@2x.png

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

●Max Potential First Input Delay 120 ms

●Layout shift culprits

●Optimize DOM size

●LCP breakdown

●Modern HTTP

●Optimize viewport for mobile

●Minify CSS

●Minify JavaScript

●Avoids enormous network payloads Total size was 1,430 KiB

●JavaScript execution time 0.7 s

●Minimizes main-thread work 1.6 s

●Avoid long main-thread tasks 6 long tasks found

●Network Requests

●Network Round Trip Times 30 ms

●Server Backend Latencies 40 ms

●Tasks

●Diagnostics

●Metrics

●Screenshot Thumbnails

●Final Screenshot

●Script Treemap Data

●Resources Summary

●Avoid multiple page redirects

●Initial server response time was short Root document took 90 ms

●Avoid large layout shifts 1 layout shift found

○INP breakdown

○User Timing marks and measures

○Avoid non-composited animations

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.

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
Young People’s Book Prize `div.hero-card > a.hero-card__link > div.hero-card__text > h4.hero-card__title`
Climate change: evidence and causes `div.horizontal-accordion__item > div.horizontal-accordion__content > a.horizontal-accordion__link > h4.horizontal-accordion__title`

These are opportunities to improve keyboard navigation in your application.

Visible text labels that do not match the accessible name can result in a confusing experience for screen reader users. Learn more about accessible names.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Cookies \| Royal Society `div#onetrust-group-container > div#onetrust-policy > div#onetrust-policy-text > a.ot-cookie-policy-link`

○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

●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.

●`button`, `link`, and `menuitem` elements have accessible names

●ARIA attributes are used as specified for the element's role

●Elements with `role="dialog"` or `role="alertdialog"` have accessible names.

●`[aria-hidden="true"]` elements do not contain focusable descendents

●Elements use only permitted ARIA attributes

●Background and foreground colors have a sufficient contrast ratio

●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

●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

●All heading elements contain content.

○`[accesskey]` values are unique

○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

○Lists contain only `<li>` elements and script supporting elements (`<script>` and `<template>`).

○List items (`<li>`) are contained within `<ul>`, `<ol>` or `<menu>` parent elements

○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>`.

○Uses ARIA roles only on compatible elements

○Image elements do not have `[alt]` attributes that are redundant text.

○Identical links have the same purpose.

○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.

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.

Source	Description
royalsociety.org/assets/icons/favicon-32x32.png	`Failed to load resource: the server responded with a status of 404 ()`

●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

●Page has valid source maps

○Redirects HTTP traffic to HTTPS

○Use a strong HSTS policy

○Mitigate clickjacking with XFO or CSP

○Detected JavaScript libraries

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 destination	Link Text
cookiepedia.co.uk/giving-consent-to-cookies	More information

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

●Image elements have `[alt]` attributes

●Document has a valid `hreflang`

●Document has a valid `rel=canonical`

○robots.txt is valid