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Lighthouse Desktop

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

Audit breakdown by category with detailed findings.

81

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
clinicaltrials.gov/assets/images/nih-nlm-ncbi-logo.png86400.0 s230.7 KiB
cdn.ncbi.nlm.nih.gov/core/pinger/pinger.js3600.0 s29.7 KiB
/Universal-Federated-Analytics-Min.js?agency=HHS&subagenc...0.0 ms9.4 KiB
cdn.ncbi.nlm.nih.gov/core/alerts/alerts.js3600.0 s6.1 KiB
dap.digitalgov.gov/web-vitals/dist/web-vitals.attribution.iife.js0.0 ms4.5 KiB
/SIE/?Q_ZID=ZN_dikYWqsjiUWN0Q53600.0 s4.6 KiB
clinicaltrials.gov/assets/main/img/AgencyLogo.svg86400.0 s9.0 KiB
/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERS...604800.0 s35.9 KiB
/dxjsmodule/CoreModule.js?Q_CLIENTVERSION=2.46.0&Q_CLIENT...604800.0 s30.9 KiB
iad1.qualtrics.com/WRQualtricsSiteIntercept/Graphic.php?IM=IM_3xWqwNkIHc7cA0S37.0 s2.3 KiB
/dxjsmodule/FeedbackButtonModule.js?Q_CLIENTVERSION=2.46....604800.0 s19.4 KiB
/dxjsmodule/37.7ea1ffe71ad8c0799cc1.chunk.js?Q_CLIENTVERS...604800.0 s18.6 KiB
clinicaltrials.gov/assets/images/ctg-header-logo.svg86400.0 s3.4 KiB
clinicaltrials.gov/assets/images/ctg-footer-logo.svg86400.0 s1.9 KiB
/dxjsmodule/1.bc67e778235741631577.chunk.js?Q_CLIENTVERSI...604800.0 s7.1 KiB
clinicaltrials.gov/assets/images/warning.svg86400.0 s1.0 KiB
clinicaltrials.gov/assets/uswds/img/icon-https.svg86400.0 s481 B
clinicaltrials.gov/assets/uswds/img/icon-dot-gov.svg86400.0 s455 B
clinicaltrials.gov/assets/images/close.png86400.0 s368 B
clinicaltrials.gov/assets/uswds/img/us_flag_small.png86400.0 s360 B
/dxjsmodule/7.f7df015b06d8a90ce822.chunk.js?Q_CLIENTVERSI...604800.0 s1.4 KiB
clinicaltrials.gov/assets/uswds/img/usa-icons/search.svg86400.0 s300 B
clinicaltrials.gov/assets/uswds/img/usa-icons/warning.svg86400.0 s235 B
clinicaltrials.gov/assets/uswds/img/usa-icons/expand_more.svg86400.0 s234 B
clinicaltrials.gov/assets/uswds/img/usa-icons/add.svg86400.0 s233 B
clinicaltrials.gov/assets/images/glossary-panel/close-glossary-drawer.svg86400.0 s0 B
clinicaltrials.gov/assets/images/glossary-panel/open-glossary-drawer.svg86400.0 s0 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:0.12619] map[node:map[boundingRect:map[bottom:312 height:112 left:1307 right:1350 top:200 width:43] lhId:page-1-DIV nodeLabel:Show glossary path:1,HTML,1,BODY,0,DIV selector:body > div#open-glossary snippet:<div id="open-glossary" class="open-glossary" aria-describedby="glossary-result" aria-hidden="false"> type:node] score:0.12238] map[node:map[boundingRect:map[bottom:398 height:123 left:363 right:1073 top:276 width:710] lhId:page-2-DIV nodeLabel:The U.S. government does not review or approve the safety and science of all st… path:1,HTML,1,BODY,2,APP-ROOT,2,MAIN,1,CTG-HOME,0,DIV,0,DIV,0,CTG-HOME-TITLE-AND-DISCLAIMER,1,SECTION,0,CTG-DISCLAIMER,0,DIV,0,DIV,1,DIV selector:ctg-disclaimer > div > div.usa-alert > div.usa-alert__body snippet:<div _ngcontent-ng-c232542777="" class="usa-alert__body"> type:node] score:0.00381]]

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:36.43 source:map[type:text value:[unattributed]]] map[reflowTime:0.426 source:map[column:7398 line:0 type:source-location url:https://clinicaltrials.gov/chunk-PVALZXTS.js urlProvider:network]] map[reflowTime:0.258 source:map[column:26397 line:0 type:source-location url:https://clinicaltrials.gov/main-CVYC5WO6.js urlProvider:network]] map[reflowTime:0.028 source:map[column:27214 line:0 type:source-location url:https://clinicaltrials.gov/main-CVYC5WO6.js urlProvider:network]]]

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
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
cdn.ncbi.nlm.nih.gov/core/pinger/pinger.js29.7 KiB250 ms

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

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
Show glossary body > div#open-glossary
0.122
The U.S. government does not review or approve the safety and science of all st… ctg-disclaimer > div > div.usa-alert > div.usa-alert__body
0.004

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: 40 ms 88.4 KiB
URLTransfer SizeEst Savings
clinicaltrials.gov/styles-K5ERNWXN.css100.4 KiB88.4 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: 200 ms 261.4 KiB
URLTransfer SizeEst Savings
/gtag/js?id=G-DP2X732JSX&l=pingerDataLayer&cx=c&gtm=4e64h1147.5 KiB62.3 KiB
www.googletagmanager.com/gtag/js?id=G-CSLL4ZEK4L147.1 KiB62.3 KiB
www.googletagmanager.com/gtm.js?id=GTM-PC9B6M3&l=pingerDataLayer129.5 KiB60.4 KiB
clinicaltrials.gov/chunk-FOI7A4D4.js54.4 KiB29.5 KiB
clinicaltrials.gov/chunk-J3DBZWUT.js70.4 KiB25.7 KiB
/dxjsmodule/12.1a2b7192fd54e87d3971.chunk.js?Q_CLIENTVERS...35.7 KiB21.3 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 reasonFailure type
Pages with cache-control:no-store header cannot enter back/forward cache.Actionable
Pages whose main resource has cache-control:no-store cannot enter back/forward cache.Not actionable
Back/forward cache is disabled because some JavaScript network request received resource with Cache-Control: no-store header.Not 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
ClinicalTrials.gov logo div.grid-row > div.grid-row > div.tablet:grid-col > img.ctg-logo
clinicaltrials.gov/assets/images/ctg-footer-logo.svg
NIH National Library of Medicine, National Center for Biotechnology Information… div.grid-row > div.mobile-lg:grid-col-8 > a.logo > img.ncbi-logo
clinicaltrials.gov/assets/main/img/AgencyLogo.svg
Tell us what you think! body > div.QSIFeedbackButton > button#QSIFeedbackButton-btn > img
iad1.qualtrics.com/WRQualtricsSiteIntercept/Graphic.php?IM=IM_3xWqwNkIHc7cA0S
header.usa-banner__header > div.usa-banner__inner > div.grid-col-auto > img.usa-banner__header-flag header.usa-banner__header > div.usa-banner__inner > div.grid-col-auto > img.usa-banner__header-flag
clinicaltrials.gov/assets/uswds/img/us_flag_small.png
Disclaimer div > div.usa-alert > div > img.warning-icon
clinicaltrials.gov/assets/images/warning.svg

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

●Time to Interactive 2.3 s
●Document request latency
●Optimize DOM size
●Font display
●Improve image delivery
●LCP breakdown
●Modern HTTP
●Optimize viewport for mobile
●Minify CSS
●Minify JavaScript
●Avoids enormous network payloads Total size was 1,411 KiB
●User Timing marks and measures 53 user timings
●JavaScript execution time 0.7 s
●Minimizes main-thread work 1.3 s
●Avoid long main-thread tasks 3 long tasks found
●Network Requests
●Network Round Trip Times 120 ms
●Server Backend Latencies 140 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 140 ms
○INP breakdown
○LCP request discovery
○Avoid non-composited animations
97

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
(all filters optional) ctg-home-search-panel > div.home-search-panel > div.search-panel-header > span

These are opportunities to improve the legibility of your content.

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
Data and API nav.max-width > ul.usa-nav__primary > li.usa-nav__primary-item > button.usa-accordion__button
My Saved Studies (0) nav.max-width > ul.usa-nav__primary > li.usa-nav__primary-item > button.button-display
The U.S. government does not review or approve the safety and science of all st… div.usa-alert__body > div.usa-accordion > div.usa-accordion__heading > button.usa-accordion__button
○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
●`[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 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
○`[accesskey]` values are unique
○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.
○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.
100

Best Practices

●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
●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
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`

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