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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.

86

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
www.python.org/static/stylesheets/style.c4f369bed0d3.css604800.0 s122.7 KiB
media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js3600.0 s8.7 KiB
www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woff604800.0 s29.5 KiB
www.python.org/static/fonts/FluxBold.3fd71a747d5c.woff604800.0 s28.6 KiB
www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woff604800.0 s27.5 KiB
www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woff604800.0 s26.0 KiB
www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woff604800.0 s25.8 KiB
www.python.org/static/stylesheets/mq.a4feecea96fa.css604800.0 s17.3 KiB
www.python.org/static/img/python-logo.png604800.0 s15.6 KiB
www.python.org/static/img/python-logo-large.c36dccadd999.png?1694722768604800.0 s12.9 KiB
www.python.org/static/js/main-min.e1f3949ae225.js604800.0 s9.9 KiB
www.python.org/static/js/libs/masonry.pkgd.min.js604800.0 s8.0 KiB
www.python.org/static/stylesheets/font-awesome.bf0c425cdb73.css604800.0 s7.2 KiB
www.python.org/static/js/libs/modernizr.js604800.0 s5.1 KiB
www.python.org/static/js/libs/html-includes.js604800.0 s317 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:0.257904] map[node:map[boundingRect:map[bottom:969 height:237 left:99 right:1251 top:732 width:1152] lhId:page-2-DIV nodeLabel:Get Started Whether you're new to programming or an experienced developer, it'… path:1,HTML,1,BODY,0,DIV,5,DIV,1,DIV,0,SECTION,1,DIV selector:div#content > div.container > section.main-content > div.row snippet:<div class="row"> type:node] score:0.149392 subItems:map[items:[map[cause:Web font extra:map[type:url value:https://www.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woff]] map[cause:Web font extra:map[type:url value:https://www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woff]] map[cause:Web font extra:map[type:url value:https://www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woff]] map[cause:Web font extra:map[type:url value:https://www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woff]] map[cause:Web font extra:map[type:url value:https://www.python.org/static/fonts/FluxBold.3fd71a747d5c.woff]]] type:subitems]] map[node:map[boundingRect:map[bottom:1923 height:1315 left:0 right:1350 top:609 width:1350] lhId:page-7-DIV nodeLabel: Join us in Long Beach, CA starting May 13, 2026. Grab your ticket and discount… path:1,HTML,1,BODY,0,DIV,5,DIV selector:body#homepage > div#touchnav-wrapper > div#content snippet:<div id="content" class="content-wrapper"> type:node] score:0.108512]]

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:12.911 source:map[column:9771 line:2 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.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:43.865 source:map[type:text value:[unattributed]]] map[reflowTime:0.564 source:map[column:21651 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.295 source:map[column:21748 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.186 source:map[column:21978 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.152 source:map[column:22405 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.211 source:map[column:22560 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.206 source:map[column:22705 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.689 source:map[column:6429 line:8 type:source-location url:https://www.python.org/static/js/libs/masonry.pkgd.min.js urlProvider:network]] map[reflowTime:0.433 source:map[column:6586 line:8 type:source-location url:https://www.python.org/static/js/libs/masonry.pkgd.min.js urlProvider:network]] map[reflowTime:0.274 source:map[column:6624 line:8 type:source-location url:https://www.python.org/static/js/libs/masonry.pkgd.min.js urlProvider:network]] map[reflowTime:3.913 source:map[column:75860 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:3.47 source:map[column:3477 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:1.63 source:map[column:3463 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.888 source:map[column:75206 line:1 type:source-location url:https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js urlProvider:network]] map[reflowTime:0.228 source:map[column:787 line:0 type:source-location url:https://analytics.python.org/js/script.file-downloads.outbound-links.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.

URLResource SizeEst Savings
python™ div.container > div.site-headline > a > img.python-logo
www.python.org/static/img/python-logo.png15.4 KiB11.6 KiB

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

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
ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.css8.8 KiB209 ms
www.python.org/static/stylesheets/style.c4f369bed0d3.css122.7 KiB240 ms
www.python.org/static/stylesheets/mq.a4feecea96fa.css17.3 KiB
www.python.org/static/js/libs/modernizr.js5.1 KiB
www.python.org/static/stylesheets/font-awesome.bf0c425cdb73.css7.2 KiB

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.python.org/static/fonts/SourceSansPro-Regular-webfont.fd0d51605201.woff10 ms
www.python.org/static/fonts/SourceSansPro-Bold-webfont.be855452e565.woff10 ms
www.python.org/static/fonts/SourceSansPro-It-webfont.1aa29ac0f190.woff10 ms
www.python.org/static/fonts/FluxBold.3fd71a747d5c.woff10 ms
www.python.org/static/fonts/FluxRegular.f5549a4fe75f.woff5.0 ms

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

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: 40 ms 24.0 KiB
URLTransfer SizeEst Savings
www.python.org/static/stylesheets/style.c4f369bed0d3.css122.7 KiB16.3 KiB
www.python.org/static/stylesheets/mq.a4feecea96fa.css17.3 KiB7.7 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: 80 ms 125.5 KiB
URLTransfer SizeEst Savings
www.python.org/static/stylesheets/style.c4f369bed0d3.css122.5 KiB111.3 KiB
www.python.org/static/stylesheets/mq.a4feecea96fa.css17.2 KiB14.3 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: 40 ms 59.2 KiB
URLTransfer SizeEst Savings
ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js66.4 KiB59.2 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 2.2 KiB
URLTransfer SizeEst Savings
www.python.org/static/js/main-min.e1f3949ae225.js9.7 KiB2.2 KiB

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

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
Get Started Whether you're new to programming or an experienced developer, it'… div#content > div.container > section.main-content > div.row
0.149
Join us in Long Beach, CA starting May 13, 2026. Grab your ticket and discount… body#homepage > div#touchnav-wrapper > div#content
0.109
●Document request latency
●Optimize DOM size
●LCP breakdown
●Modern HTTP
●Optimize viewport for mobile
●Time to Interactive 0.9 s
●Max Potential First Input Delay 30 ms
●Avoids enormous network payloads Total size was 487 KiB
●JavaScript execution time 0.1 s
●Minimizes main-thread work 0.4 s
●Image elements have explicit `width` and `height`
●Page didn't prevent back/forward cache restoration
●Network Requests
●Network Round Trip Times 110 ms
●Server Backend Latencies 280 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 0 ms
○INP breakdown
○LCP request discovery
○User Timing marks and measures
○Avoid long main-thread tasks
○Avoid non-composited animations
79

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.

ARIA

Some ARIA parent roles must contain specific child roles to perform their intended accessibility functions. Learn more about roles and required children elements.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Python PSF Docs PyPI Jobs Community div#touchnav-wrapper > div#top > nav.meta-navigation > ul.menu
About Downloads Documentation Community Success Stories News Events header.main-header > div.container > nav#mainnav > ul.navigation
About Applications Quotes Getting Started Help Python Brochure Downloads All re… footer#site-map > div.main-footer-links > div.container > ul#container
Help & General Contact Diversity Initiatives Submit Website Bug Status footer#site-map > div.site-base > div.container > ul.footer-links

Some ARIA child roles must be contained by specific parent roles to properly perform their intended accessibility functions. Learn more about ARIA roles and required parent element.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Applications ul#container > li.tier-1 > ul.subnav > li.tier-2
Quotes ul#container > li.tier-1 > ul.subnav > li.tier-2
Getting Started ul#container > li.tier-1 > ul.subnav > li.tier-2
Help ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Brochure ul#container > li.tier-1 > ul.subnav > li.tier-2
All releases ul#container > li.tier-1 > ul.subnav > li.tier-2
Source code ul#container > li.tier-1 > ul.subnav > li.tier-2
Windows ul#container > li.tier-1 > ul.subnav > li.tier-2
macOS ul#container > li.tier-1 > ul.subnav > li.tier-2
Android ul#container > li.tier-1 > ul.subnav > li.tier-2
Other Platforms ul#container > li.tier-1 > ul.subnav > li.tier-2
License ul#container > li.tier-1 > ul.subnav > li.tier-2
Alternative Implementations ul#container > li.tier-1 > ul.subnav > li.tier-2
Docs ul#container > li.tier-1 > ul.subnav > li.tier-2
Audio/Visual Talks ul#container > li.tier-1 > ul.subnav > li.tier-2
Beginner's Guide ul#container > li.tier-1 > ul.subnav > li.tier-2
FAQ ul#container > li.tier-1 > ul.subnav > li.tier-2
Non-English Docs ul#container > li.tier-1 > ul.subnav > li.tier-2
PEP Index ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Books ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Essays ul#container > li.tier-1 > ul.subnav > li.tier-2
Diversity ul#container > li.tier-1 > ul.subnav > li.tier-2
Mailing Lists ul#container > li.tier-1 > ul.subnav > li.tier-2
IRC ul#container > li.tier-1 > ul.subnav > li.tier-2
Forums ul#container > li.tier-1 > ul.subnav > li.tier-2
PSF Annual Impact Report ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Conferences ul#container > li.tier-1 > ul.subnav > li.tier-2
Special Interest Groups ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Logo ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Wiki ul#container > li.tier-1 > ul.subnav > li.tier-2
Code of Conduct ul#container > li.tier-1 > ul.subnav > li.tier-2
Community Awards ul#container > li.tier-1 > ul.subnav > li.tier-2
Get Involved ul#container > li.tier-1 > ul.subnav > li.tier-2
Shared Stories ul#container > li.tier-1 > ul.subnav > li.tier-2
Arts ul#container > li.tier-1 > ul.subnav > li.tier-2
Business ul#container > li.tier-1 > ul.subnav > li.tier-2
Education ul#container > li.tier-1 > ul.subnav > li.tier-2
Engineering ul#container > li.tier-1 > ul.subnav > li.tier-2
Government ul#container > li.tier-1 > ul.subnav > li.tier-2
Scientific ul#container > li.tier-1 > ul.subnav > li.tier-2
Software Development ul#container > li.tier-1 > ul.subnav > li.tier-2
Python News ul#container > li.tier-1 > ul.subnav > li.tier-2
PSF Newsletter ul#container > li.tier-1 > ul.subnav > li.tier-2
PSF News ul#container > li.tier-1 > ul.subnav > li.tier-2
PyCon US News ul#container > li.tier-1 > ul.subnav > li.tier-2
News from the Community ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Events ul#container > li.tier-1 > ul.subnav > li.tier-2
User Group Events ul#container > li.tier-1 > ul.subnav > li.tier-2
Python Events Archive ul#container > li.tier-1 > ul.subnav > li.tier-2
User Group Events Archive ul#container > li.tier-1 > ul.subnav > li.tier-2
Submit an Event ul#container > li.tier-1 > ul.subnav > li.tier-2
Developer's Guide ul#container > li.tier-1 > ul.subnav > li.tier-2
Issue Tracker ul#container > li.tier-1 > ul.subnav > li.tier-2
python-dev list ul#container > li.tier-1 > ul.subnav > li.tier-2
Core Mentorship ul#container > li.tier-1 > ul.subnav > li.tier-2
Report a Security Issue ul#container > li.tier-1 > ul.subnav > li.tier-2

These are opportunities to improve the usage of ARIA in your application which may enhance the experience for users of assistive technology, like a screen reader.

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
div.options-bar > form.search-the-site > fieldset > input#id-search-field div.options-bar > form.search-the-site > fieldset > input#id-search-field
# Python 3: Fibonacci series up to n >>> def fib(n): >>> a, b = 0, 1 >>> … li.flex-active-slide > div.slide-code > pre > code
# Python 3: Fibonacci series up to n div.slide-code > pre > code > span.comment
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 div.slide-code > pre > code > span.output
About div.container > ul#container > li.tier-1 > a
Downloads div.container > ul#container > li.tier-1 > a
Documentation div.container > ul#container > li.tier-1 > a
Community div.container > ul#container > li.tier-1 > a
Success Stories div.container > ul#container > li.tier-1 > a
News div.container > ul#container > li.tier-1 > a
Events div.container > ul#container > li.tier-1 > a
Contributing div.container > ul#container > li.tier-1 > a

These are opportunities to improve the legibility of your content.

Tables and lists

Screen readers have a specific way of announcing lists. Ensuring proper list structure aids screen reader output. Learn more about proper list structure.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Applications Quotes Getting Started Help Python Brochure div.container > ul#container > li.tier-1 > ul.subnav
All releases Source code Windows macOS Android Other Platforms License Alternat… div.container > ul#container > li.tier-1 > ul.subnav
Docs Audio/Visual Talks Beginner's Guide FAQ Non-English Docs PEP Index Python … div.container > ul#container > li.tier-1 > ul.subnav
Diversity Mailing Lists IRC Forums PSF Annual Impact Report Python Conferences … div.container > ul#container > li.tier-1 > ul.subnav
Arts Business Education Engineering Government Scientific Software Development div.container > ul#container > li.tier-1 > ul.subnav
Python News PSF Newsletter PSF News PyCon US News News from the Community div.container > ul#container > li.tier-1 > ul.subnav
Python Events User Group Events Python Events Archive User Group Events Archive… div.container > ul#container > li.tier-1 > ul.subnav
Developer's Guide Issue Tracker python-dev list Core Mentorship Report a Securi… div.container > ul#container > li.tier-1 > ul.subnav

Screen readers require list items (`<li>`) to be contained within a parent `<ul>`, `<ol>` or `<menu>` to be announced properly. Learn more about proper list structure.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
Python div#top > nav.meta-navigation > ul.menu > li.python-meta
PSF div#top > nav.meta-navigation > ul.menu > li.psf-meta
Docs div#top > nav.meta-navigation > ul.menu > li.docs-meta
PyPI div#top > nav.meta-navigation > ul.menu > li.pypi-meta
Jobs div#top > nav.meta-navigation > ul.menu > li.jobs-meta
Community div#top > nav.meta-navigation > ul.menu > li.shop-meta
About div.container > nav#mainnav > ul.navigation > li#about
Downloads div.container > nav#mainnav > ul.navigation > li#downloads
Documentation div.container > nav#mainnav > ul.navigation > li#documentation
Community div.container > nav#mainnav > ul.navigation > li#community
Success Stories div.container > nav#mainnav > ul.navigation > li#success-stories
News div.container > nav#mainnav > ul.navigation > li#news
Events div.container > nav#mainnav > ul.navigation > li#events
About Applications Quotes Getting Started Help Python Brochure div.main-footer-links > div.container > ul#container > li.tier-1
Downloads All releases Source code Windows macOS Android Other Platforms Licens… div.main-footer-links > div.container > ul#container > li.tier-1
Documentation Docs Audio/Visual Talks Beginner's Guide FAQ Non-English Docs PEP… div.main-footer-links > div.container > ul#container > li.tier-1
Community Diversity Mailing Lists IRC Forums PSF Annual Impact Report Python Co… div.main-footer-links > div.container > ul#container > li.tier-1
Success Stories Arts Business Education Engineering Government Scientific Softw… div.main-footer-links > div.container > ul#container > li.tier-1
News Python News PSF Newsletter PSF News PyCon US News News from the Community div.main-footer-links > div.container > ul#container > li.tier-1
Events Python Events User Group Events Python Events Archive User Group Events … div.main-footer-links > div.container > ul#container > li.tier-1
Contributing Developer's Guide Issue Tracker python-dev list Core Mentorship Re… div.main-footer-links > div.container > ul#container > li.tier-1
Help & General Contact div.site-base > div.container > ul.footer-links > li.tier-1
Diversity Initiatives div.site-base > div.container > ul.footer-links > li.tier-1
Submit Website Bug div.site-base > div.container > ul.footer-links > li.tier-1
Status div.site-base > div.container > ul.footer-links > li.tier-1

These are opportunities to improve the experience of reading tabular or list data using assistive technology, like a screen reader.

Navigation

A value greater than 0 implies an explicit navigation ordering. Although technically valid, this often creates frustrating experiences for users who rely on assistive technologies. Learn more about the `tabindex` attribute.

Why this matters

Performance issues directly impact user engagement and conversion rates.

Failing Elements
div.options-bar > form.search-the-site > fieldset > input#id-search-field div.options-bar > form.search-the-site > fieldset > input#id-search-field
GO div.options-bar > form.search-the-site > fieldset > button#submit

These are opportunities to improve keyboard navigation in your application.

○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
●ARIA `treeitem` elements have accessible names
●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
●Touch targets have sufficient size and spacing.
●Cells in a `<table>` element that use the `[headers]` attribute refer to table cells within the same table.
●Heading elements appear in a sequentially-descending order
●Document has a main landmark.
●Deprecated ARIA roles were not used
●Identical links have the same purpose.
○`[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 the `role=text` attribute do not have focusable descendents.
○ARIA toggle fields have accessible names
○ARIA `tooltip` 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.
○`<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.
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
media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js
Error: No ad placements found. at w (https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js:1:11867) at https://media.ethicalads.io/media/client/v1.4.0/ethicalads.min.js:1:12977
●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.

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 destinationLink Text
www.python.org/doc/Learn More
blog.python.org/More
www.python.org/events/calendars/More
www.python.org/success-stories/More
www.python.org/about/appsMore
www.python.org/psf/Learn more

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

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