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
assets.adobedtm.com/c2b29812570b/d7d2d2aae38a/launch-e413b49718e8.min.js	3600.0 s	71.6 KiB
www.nhm.ac.uk/_next/static/chunks/pages/_app-53d16d5b935d3f3a.js	604800.0 s	486.2 KiB
/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	43200.0 s	81.1 KiB
/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	43200.0 s	66.7 KiB
/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	43200.0 s	49.7 KiB
/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	43200.0 s	29.1 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/resized...	604800.0 s	121.0 KiB
www.nhm.ac.uk/fonts/NHMWallopText.woff2	604800.0 s	90.7 KiB
www.nhm.ac.uk/fonts/NHMWallopHeadline.woff2	604800.0 s	88.5 KiB
www.nhm.ac.uk/cdn-cgi/challenge-platform/h/b/scripts/jsd/0b8fb825cb67/main.js?	14400.0 s	12.6 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/fern-fo...	604800.0 s	48.3 KiB
www.nhm.ac.uk/_next/static/chunks/framework-64ad27b21261a9ce.js	604800.0 s	44.0 KiB
/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da177152312...	86400.0 s	10.7 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/sequoia...	604800.0 s	40.2 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/blue-wh...	604800.0 s	39.1 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/sophie-...	604800.0 s	37.5 KiB
/content/dam/nhm-www/visit/Exhibitions/wpy61/wpy61-jelly-...	604800.0 s	34.9 KiB
/content/dam/nhm-www/discover/wpy-peoples-choice-61/PC04-...	604800.0 s	34.4 KiB
www.nhm.ac.uk/_next/static/chunks/main-4b423ec82b590a3f.js	604800.0 s	33.4 KiB
/content/dam/nhm-www/home/2025-new-home-page-test/t-rex-f...	604800.0 s	32.7 KiB
www.nhm.ac.uk/_next/static/css/b1b78ee8badc65ec.css	604800.0 s	21.2 KiB
/c2b29812570b/d7d2d2aae38a/d17eff647a94/RC979da14378d3423...	3600.0 s	2.1 KiB
www.nhm.ac.uk/scripts/early-analytics.js	604800.0 s	16.1 KiB
www.nhm.ac.uk/_next/static/chunks/886-7d6523c1202edc02.js	604800.0 s	10.3 KiB
/c2b29812570b/d7d2d2aae38a/d17eff647a94/RCdf65f326e593468...	3600.0 s	1.2 KiB
/c2b29812570b/d7d2d2aae38a/d17eff647a94/RC672aeff480d24e6...	3600.0 s	1.0 KiB
www.nhm.ac.uk/_next/static/chunks/2-3a63044a420995fc.js	604800.0 s	6.2 KiB
/c2b29812570b/d7d2d2aae38a/d17eff647a94/RC1fdb346bf3ea47f...	3600.0 s	771 B
www.nhm.ac.uk/_next/static/chunks/webpack-b7749b26d5a76fc9.js	604800.0 s	1.8 KiB
www.nhm.ac.uk/_next/static/css/caab7f82a60735b8.css	604800.0 s	1.3 KiB
www.nhm.ac.uk/_next/static/chunks/pages/index-b0d422fcae8e50d7.js	604800.0 s	698 B
www.nhm.ac.uk/_next/static/jIUk2ai3GE_NNa0A2G68-/_buildManifest.js	604800.0 s	534 B
www.nhm.ac.uk/_next/static/jIUk2ai3GE_NNa0A2G68-/_ssgManifest.js	604800.0 s	136 B
www.nhm.ac.uk/_next/static/chunks/pages/%5B...path%5D-f6e8026219925700.js	604800.0 s	0 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.

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:41.833 source:map[column:137981 line:1 type:source-location url:https://www.nhm.ac.uk/_next/static/chunks/framework-64ad27b21261a9ce.js 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:89.56 source:map[type:text value:[unattributed]]] map[reflowTime:41.833 source:map[column:119358 line:51 type:source-location url:https://www.nhm.ac.uk/_next/static/chunks/pages/_app-53d16d5b935d3f3a.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
Fern, our big bronze dinosaur, stands tall in front of our building, his neck a… `div.overflow-hidden > figure.absolute > picture > img.absolute`	/content/dam/nhm-www/home/2025-new-home-page-test/resized...	120.6 KiB	61.9 KiB
Sir David Attenborough smiles, sitting in front of screens showing chimpanzees … `div#EXH-OURSTORYG > div.aspect-video > figure.h-full > img.w-full`	/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	80.8 KiB	45.4 KiB
li.relative > figure.h-auto > picture > img.h-auto `li.relative > figure.h-auto > picture > img.h-auto`	/content/dam/nhm-www/home/2025-new-home-page-test/sequoia...	40.0 KiB	17.6 KiB
A boy smiles in amazement as he looks at a turtle swimming above his head, as h… `div#VON-VONADM > div.aspect-video > figure.h-full > img.w-full`	/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	49.4 KiB	16.3 KiB
A family of a mother, a father and three children sit in their pijamas on sleep… `div#VISEV-DSK > div.aspect-video > figure.h-full > img.w-full`	/_next/image?url=https%3A%2F%2Fwww.nhm.ac.uk%2Fcontent%2F...	66.4 KiB	15.0 KiB
A jellyfish swims against a green background full of smaller jellyfish `div.Tile_tile__asset__HYs46 > figure > picture > img.Image_image__dENwr`	/content/dam/nhm-www/visit/Exhibitions/wpy61/wpy61-jelly-...	34.7 KiB	13.6 KiB
A lynx balances on its rear paws while trying to catch a rodent with its front-… `div.Tile_tile__asset__HYs46 > figure > picture > img.Image_image__dENwr`	/content/dam/nhm-www/discover/wpy-peoples-choice-61/PC04-...	34.2 KiB	13.0 KiB
li.relative > figure.h-auto > picture > img.h-auto `li.relative > figure.h-auto > picture > img.h-auto`	/content/dam/nhm-www/home/2025-new-home-page-test/t-rex-f...	32.5 KiB	10.0 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-0-IMG

nodeLabel: Fern, our big bronze dinosaur, stands tall in front of our building, his neck a…

path: 1,HTML,1,BODY,1,DIV,0,DIV,2,MAIN,0,SECTION,1,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,FIGURE,0,PICTURE,8,IMG

selector: div.overflow-hidden > figure.absolute > picture > img.absolute

snippet: <img class="absolute inset-0 w-full h-full object-cover" loading="lazy" src="https://www.nhm.ac.uk/content/dam/nhm-www/home/2025-new-home-page-test/res…" width="2300" height="1380" alt="Fern, our big bronze dinosaur, stands tall in front of our building, his n…">

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

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: 758 ms

URL	Time Spent
nhm.ac.uk/	758 ms
www.nhm.ac.uk/	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.

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: 150 ms 16.0 KiB

URL	Transfer Size	Est Savings
www.nhm.ac.uk/_next/static/css/b1b78ee8badc65ec.css	21.0 KiB	16.0 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: 1.8 s 487.4 KiB

URL	Transfer Size	Est Savings
www.nhm.ac.uk/_next/static/chunks/pages/_app-53d16d5b935d3f3a.js	486.1 KiB	362.5 KiB
www.googletagmanager.com/gtm.js?id=GTM-5TDGNT	179.7 KiB	91.2 KiB
assets.adobedtm.com/c2b29812570b/d7d2d2aae38a/launch-e413b49718e8.min.js	71.3 KiB	33.7 KiB

Consider reducing the time spent parsing, compiling, and executing JS. You may find delivering smaller JS payloads helps with this. Learn how to reduce Javascript execution time.

Why this matters

Performance issues directly impact user engagement and conversion rates.

URL	Total CPU Time	Script Evaluation	Script Parse
www.nhm.ac.uk/	999 ms	67 ms	3.0 ms
www.nhm.ac.uk/_next/static/chunks/framework-64ad27b21261a9ce.js	950 ms	683 ms	18 ms
www.nhm.ac.uk/_next/static/chunks/pages/_app-53d16d5b935d3f3a.js	450 ms	230 ms	217 ms
www.googletagmanager.com/gtm.js?id=GTM-5TDGNT	327 ms	220 ms	72 ms
Unattributable	301 ms	8.9 ms	0.0 ms
www.nhm.ac.uk/cdn-cgi/challenge-platform/scripts/jsd/main.js	279 ms	267 ms	3.7 ms
assets.adobedtm.com/c2b29812570b/d7d2d2aae38a/launch-e413b49718e8.min.js	216 ms	171 ms	37 ms
www.nhm.ac.uk/_next/static/chunks/main-4b423ec82b590a3f.js	78 ms	61 ms	15 ms
www.nhm.ac.uk/scripts/early-analytics.js	59 ms	48 ms	6.9 ms

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.

Category	Time Spent
Script Evaluation	1.9 s
Style & Layout	822 ms
Other	506 ms
Script Parsing & Compilation	390 ms
Parse HTML & CSS	127 ms
Rendering	84 ms
Garbage Collection	30 ms

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

●Layout shift culprits

●Optimize DOM size

●Font display

●LCP breakdown

●Modern HTTP

●Render blocking requests

●Optimize viewport for mobile

●Minify CSS

●Minify JavaScript

●Avoids enormous network payloads Total size was 1,769 KiB

●User Timing marks and measures 4 user timings

●Avoid long main-thread tasks 14 long tasks found

●Avoid non-composited animations 3 animated elements found

●Image elements have explicit `width` and `height`

●Page didn't prevent back/forward cache restoration

●Network Requests

●Network Round Trip Times 0 ms

●Server Backend Latencies 70 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

100

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.

○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.

●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

●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

●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.

●Heading elements appear in a sequentially-descending order

●Document has a main landmark.

●Deprecated ARIA roles were not used

●ARIA IDs are unique

○`[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

○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.

○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.

Best Practices

General

Deprecated APIs will eventually be removed from the browser. Learn more about deprecated APIs.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Deprecation / Warning	Source
SharedStorage	www.nhm.ac.uk/cdn-cgi/challenge-platform/scripts/jsd/main.js
StorageType.persistent is deprecated. Please use standardized navigator.storage instead.	www.nhm.ac.uk/cdn-cgi/challenge-platform/scripts/jsd/main.js
Fledge	www.nhm.ac.uk/cdn-cgi/challenge-platform/scripts/jsd/main.js

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.nhm.ac.uk/_next/static/chunks/pages/_app-53d16d5b935d3f3a.js

●Uses HTTPS

●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

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`