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
/portal/portal3rc.fcgi/rlib/js/InstrumentOmnitureBaseJS/I...	7200.0 s	29.5 KiB
/Universal-Federated-Analytics-Min.js?agency=HHS&subagenc...	0.0 ms	9.4 KiB
www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg	0.0 ms	9.0 KiB
www.ncbi.nlm.nih.gov/home/legacy/page.css	0.0 ms	8.9 KiB
dap.digitalgov.gov/web-vitals/dist/web-vitals.attribution.iife.js	0.0 ms	4.5 KiB
www.ncbi.nlm.nih.gov/home/images/icons/analyze.svg	0.0 ms	3.7 KiB
/SIE/?Q_ZID=ZN_dikYWqsjiUWN0Q5	3600.0 s	4.6 KiB
/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERS...	604800.0 s	35.8 KiB
/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENT...	604800.0 s	30.9 KiB
script.crazyegg.com/pages/scripts/0027/2050.js	300.0 s	2.7 KiB
www.ncbi.nlm.nih.gov/home/components/normalize-css/normalize.css	0.0 ms	2.6 KiB
/dxjsmodule/37.7ea1ffe71ad8c0799cc1.chunk.js?Q_CLIENTVERS...	604800.0 s	18.6 KiB
www.ncbi.nlm.nih.gov/home/components/ncbi-standards/standard_base.css	0.0 ms	1.7 KiB
www.ncbi.nlm.nih.gov/home/images/icons/research.svg	0.0 ms	993 B
www.ncbi.nlm.nih.gov/home/images/icons/learn.svg	0.0 ms	889 B
www.ncbi.nlm.nih.gov/home/homepage.css	0.0 ms	838 B
/dxjsmodule/1.bc67e778235741631577.chunk.js?Q_CLIENTVERSI...	604800.0 s	7.1 KiB
www.ncbi.nlm.nih.gov/coreutils/uswds/img/favicons/favicon-57.png	0.0 ms	587 B
www.ncbi.nlm.nih.gov/home/images/icons/submit.svg	0.0 ms	459 B
www.ncbi.nlm.nih.gov/home/images/icons/download.svg	0.0 ms	456 B
www.ncbi.nlm.nih.gov/home/images/icons/develop.svg	0.0 ms	435 B
www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-dot-gov.svg	0.0 ms	427 B
www.ncbi.nlm.nih.gov/coreutils/uswds/img/angle-arrow-down-primary.svg	0.0 ms	378 B
www.ncbi.nlm.nih.gov/coreutils/uswds/img/icon-https.svg	0.0 ms	363 B
www.ncbi.nlm.nih.gov/home/new_grid.css	0.0 ms	327 B
/dxjsmodule/7.f7df015b06d8a90ce822.chunk.js?Q_CLIENTVERSI...	604800.0 s	1.4 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:402.1220009765625 label:Time to first byte subpart:timeToFirstByte] map[duration:13.8519990234375 label:Resource load delay subpart:resourceLoadDelay] map[duration:404.862 label:Resource load duration subpart:resourceLoadDuration] map[duration:1762.047 label:Element render delay subpart:elementRenderDelay]]

lhId: page-0-IMG

nodeLabel: NIH NLM Logo

path: 1,HTML,1,BODY,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,2,HEADER,0,DIV,0,DIV,0,DIV,0,A,0,IMG

selector: div.usa-width-one-whole > div.ncbi-header__logo > a.logo > img

snippet: <img src="https://www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg" alt="NIH NLM Logo">

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: NIH NLM Logo

path: 1,HTML,1,BODY,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,0,DIV,2,HEADER,0,DIV,0,DIV,0,DIV,0,A,0,IMG

selector: div.usa-width-one-whole > div.ncbi-header__logo > a.logo > img

snippet: <img src="https://www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg" alt="NIH NLM Logo">

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
www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js	182.7 KiB	995 ms
www.ncbi.nlm.nih.gov/home/legacy/page.css	8.9 KiB
www.ncbi.nlm.nih.gov/home/components/ncbi-standards/standard_base.css	1.7 KiB
www.ncbi.nlm.nih.gov/home/components/normalize-css/normalize.css	2.6 KiB
www.ncbi.nlm.nih.gov/home/homepage.css	838 B	249 ms
www.ncbi.nlm.nih.gov/home/new_grid.css	327 B

Tap interactions may be delayed by up to 300 ms if the viewport is not optimized for mobile.

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

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

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: 100 ms 15.4 KiB

URL	Transfer Size	Est Savings
www.ncbi.nlm.nih.gov/core/jig/1.15.6/css/jig.min.css	15.6 KiB	15.4 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: 2.4 s 401.5 KiB

URL	Transfer Size	Est Savings
www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js	182.6 KiB	142.2 KiB
/gtag/js?id=G-DP2X732JSX&l=pingerDataLayer&cx=c&gtm=4e64h1	147.5 KiB	62.4 KiB
www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L	147.1 KiB	62.4 KiB
www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer	129.6 KiB	60.4 KiB
/pages/versioned/common-scripts/4ce8c7df8d425cc5046457682...	55.1 KiB	29.8 KiB
/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERS...	35.7 KiB	22.3 KiB
/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENT...	30.9 KiB	21.9 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.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L	338 ms	291 ms	44 ms
www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js	316 ms	194 ms	67 ms
Unattributable	303 ms	9.6 ms	0.0 ms
/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERS...	280 ms	249 ms	14 ms
/pages/versioned/common-scripts/4ce8c7df8d425cc5046457682...	244 ms	212 ms	18 ms
/gtag/js?id=G-DP2X732JSX&l=pingerDataLayer&cx=c&gtm=4e64h1	227 ms	190 ms	35 ms
www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer	211 ms	176 ms	33 ms
/portal/portal3rc.fcgi/rlib/js/InstrumentOmnitureBaseJS/I...	161 ms	73 ms	11 ms
www.ncbi.nlm.nih.gov/	75 ms	7.2 ms	2.9 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	1.6 s
Other	348 ms
Script Parsing & Compilation	254 ms
Style & Layout	135 ms
Parse HTML & CSS	34 ms
Rendering	26 ms
Garbage Collection	16 ms

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 2.8 KiB

URL	Transfer Size	Est Savings
www.ncbi.nlm.nih.gov/portal/portal3rc.fcgi/static/js/hfjs2.js	5.1 KiB	2.8 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
NIH NLM Logo `div.usa-width-one-whole > div.ncbi-header__logo > a.logo > img`	www.ncbi.nlm.nih.gov/coreutils/nwds/img/logos/AgencyLogo.svg
section.action_bar > a#home_submit > div.col > img.gray-light `section.action_bar > a#home_submit > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/submit.svg
section.action_bar > a#home_download > div.col > img.gray-light `section.action_bar > a#home_download > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/download.svg
section.action_bar > a#home_learn > div.col > img.gray-light `section.action_bar > a#home_learn > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/learn.svg
section.action_bar > a#home_develop > div.col > img.gray-light `section.action_bar > a#home_develop > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/develop.svg
section.action_bar > a#home_analyze > div.col > img.gray-light `section.action_bar > a#home_analyze > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/analyze.svg
section.action_bar > a#home_research > div.col > img.gray-light `section.action_bar > a#home_research > div.col > img.gray-light`	www.ncbi.nlm.nih.gov/home/images/icons/research.svg
U.S. flag `div.usa-accordion > header.usa-banner-header > div.usa-grid > img`	www.ncbi.nlm.nih.gov/coreutils/uswds/img/favicons/favicon-57.png
Clear input `div.nowrap > div.jig-ncbiclearbutton-wrap > a.reset > img`	www.ncbi.nlm.nih.gov/core/jig/1.15.6/img/clear.png

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

●Layout shift culprits

●Document request latency

●Optimize DOM size

●Font display

●Forced reflow

●Improve image delivery

●Modern HTTP

●Minify CSS

●Avoids enormous network payloads Total size was 896 KiB

●User Timing marks and measures 14 user timings

●Avoid long main-thread tasks 11 long tasks found

●Page didn't prevent back/forward cache restoration

●Network Requests

●Network Round Trip Times 100 ms

●Server Backend Latencies 60 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 200 ms

○INP breakdown

○Avoid non-composited animations

○Avoid large layout shifts

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
20 Apr 2026 `ul.rss_items > li#ui-ncbiexpander-2 > div.expanderWrapper > p.date`
Average Nucleotide Identity (ANI) analysis is a useful tool to verify taxonomic… `ul.rss_items > li#ui-ncbiexpander-2 > div.expanderWrapper > p.desc`
15 Apr 2026 `ul.rss_items > li#ui-ncbiexpander-3 > div.expanderWrapper > p.date`
If you use NCBI’s MedGen then you probably know it is your one-stop-shop for ac… `ul.rss_items > li#ui-ncbiexpander-3 > div.expanderWrapper > p.desc`
09 Apr 2026 `ul.rss_items > li#ui-ncbiexpander-4 > div.expanderWrapper > p.date`
Download the updated bacterial and archaeal reference genome collection! We bui… `ul.rss_items > li#ui-ncbiexpander-4 > div.expanderWrapper > p.desc`

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
Accessibility `div.row > div.col-lg-3 > p > a.text-white`
Careers `div.row > div.col-lg-3 > p > a.text-white`

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

●Buttons have an accessible name

●Image elements have `[alt]` attributes

●Form elements have associated labels

●Select elements have associated label elements.

●`[accesskey]` values are unique

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

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

●Elements use only permitted ARIA attributes

●Document has a `<title>` element

●`<html>` element has a `[lang]` attribute

●`<html>` element has a valid value for its `[lang]` attribute

●Links 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

●Heading elements appear in a sequentially-descending order

●Deprecated ARIA roles were not used

●Identical links have the same purpose.

○`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

○Links are distinguishable without relying on color.

○The document does not use `<meta http-equiv="refresh">`

○`[user-scalable="no"]` is not used in the `<meta name="viewport">` element and the `[maximum-scale]` attribute is not less than 5.

○`<object>` elements have alternate text

○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.

Best Practices

User Experience

Image natural dimensions should be proportional to the display size and the pixel ratio to maximize image clarity. Learn how to provide responsive images.

Why this matters

Performance issues directly impact user engagement and conversion rates.

	URL	Displayed size	Actual size	Expected size
Clear input `div.nowrap > div.jig-ncbiclearbutton-wrap > a.reset > img`	www.ncbi.nlm.nih.gov/core/jig/1.15.6/img/clear.png	14 x 14	14 x 14	21 x 21

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	Map URL
www.ncbi.nlm.nih.gov/core/jig/1.15.6/js/jig.min.js
/Universal-Federated-Analytics-Min.js?agency=HHS&subagenc...	dap.digitalgov.gov/Federated.js.map

●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

●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

●Ensure proper origin isolation with COOP

●Mitigate DOM-based XSS with Trusted Types

●Detected JavaScript libraries

○Redirects HTTP traffic to HTTPS

○Use a strong HSTS policy

○Mitigate clickjacking with XFO or CSP

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

Meta descriptions may be included in search results to concisely summarize page content. Learn more about the meta description.

Why this matters

Performance issues directly impact user engagement and conversion rates.

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

●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`