Accessibility

· 13 checks — Landmarks, headings, alt text, forms, and link quality rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Checks

5 PASS 2 REVIEW 6 FIX

Alt Text Quality

Action

9 of 23 images have issues

FIX

9 of 23 images have issues

9 image(s) missing alt attribute

Images without alt text are invisible to screen readers.

9 image-in-link without alt text

An image inside a link with no alt creates an empty link.

14 image(s) with good alt text

23 images 14 good alt text 9 missing

Issue	Count
missing	9 image(s)

Images without alt text are invisible to screen readers.

Why this matters

Each image without alt text is a WCAG 1.1.1 failure — invisible to screen-reader users, lost from Google Image Search.

Learn more ▾

WCAG 2.1 Level A requires text alternatives for non-decorative images. Empty alt='' is fine for decorative; meaningful images need descriptive text. Common fixes: CMS audit + bulk add, build-time linter (alt-text-required ESLint rule), CI gate on Lighthouse a11y score.

Source: WCAG 2.1 SC 1.1.1 / WebAIM Million Report

An image inside a link with no alt creates an empty link.

Why this matters

Image-only links with no alt create empty links — screen-reader users hear 'link' with no destination context.

Learn more ▾

An <a><img></a> with no img alt is the worst-case for accessibility: AT announces the link but can't describe where it goes. Either add alt to the image OR add aria-label to the link.

Source: WCAG 2.1 SC 2.4.4

Favicon & Branding

Action

1 icon(s) detected

FIX

1 icon(s) detected

No favicon.ico at site root

Some older browsers, bookmark tools, and RSS readers look for /favicon.ico. Add one as a fallback.

HTML icon links detected

No apple-touch-icon detected

iOS devices use this when users add your site to their home screen. Add <link rel='apple-touch-icon' sizes='180x180' href='/apple-touch-icon.png'>.

✗ favicon.ico Missing

✓ PNG Icons Present

✗ Apple Touch Missing

✗ SVG Favicon Missing

✗ Manifest Icons Missing

✗ Multiple Sizes Missing

Web Manifest

Action

Not found

FIX

Not found

No web manifest found

No manifest at standard paths (/manifest.json, /site.webmanifest). A manifest is optional but enables PWA features like home screen installation and standalone display.

No web manifest found.

Dark Mode Support

Action

No dark mode signals

FIX

No dark mode signals

No dark mode signals detected

Consider adding CSS with @media (prefers-color-scheme: dark) and <meta name='color-scheme' content='light dark'>.

Detection limited to meta tags and inline styles

External CSS files may contain prefers-color-scheme rules not visible to this scan.

Dark ModeNo Dark Mode Detected

color-scheme meta Not set ✗Dark theme-color Not set ✗CSS indicators Not detected ✗

Detection limited to meta tags and inline styles.

Print Stylesheet

Action

No print styles

FIX

No print styles

No print-specific styles detected

When users print this page, they get the screen layout including navigation and non-essential elements. Add @media print rules to hide navigation and optimize layout for paper.

Print Stylesheet No Print Styles

Print stylesheet Not found ✗Inline @media print Not detected ✗

Landmark Structure

6 landmarks

REVIEW

6 landmarks

<main> landmark present

Multiple <main> landmarks (2 found)

A page should have only one <main> landmark.

2 <nav> landmark(s) found

2 of 2 <nav> elements are unlabeled

Multiple navigations need aria-label to distinguish them for screen readers.

No contentinfo (footer) landmark

Skip navigation link present

Page Structure — as a screen reader sees it

A page should have only one <main> landmark.

Why this matters

Multiple <main> elements violate the spec — there must be exactly one per page.

Learn more ▾

HTML5 spec: 'authors must not include more than one main element' visible to AT at the same time. Multiple <main>s confuse AT and break the 'jump to main content' shortcut. Refactor to a single <main> with nested <section>/<article>.

Source: HTML5 spec

Multiple navigations need aria-label to distinguish them for screen readers.

Why this matters

Some <nav> elements lack aria-label — screen-reader users hear 'navigation' multiple times with no way to distinguish them.

Learn more ▾

When a page has multiple <nav> regions (primary, footer, breadcrumb), each needs aria-label or aria-labelledby. AT users navigate by landmark; identical 'navigation' announcements force them to enter each one to discover purpose.

Source: WAI-ARIA Authoring Practices

404 Error Page

HTTP 404, custom page

REVIEW

HTTP 404, custom page

Correct 404 status code returned

Got: HTTP 404

Custom styled 404 page

Navigation links present on 404 page

Homepage link present on 404 page

404 Page Quality ✓ Custom 404 Page

Status Code HTTP 404 ✓Page Title Page not found · GitHub Pages ✓Custom Styling ✓Navigation ✓Homepage Link ✓Search Form ✗

Heading Hierarchy

11 headings, 1 skip(s)

PASS

11 headings, 1 skip(s)

Single H1 present

Heading level skipped: H1 → H4 (missing H2)

Skipping heading levels breaks the document outline. Screen readers may interpret missing levels as structural errors.

H1 scikit-learn
H4 Machine Learning in Python skipped
H4 Classification
H4 Regression
H4 Clustering
H4 Dimensionality reduction
H4 Model selection
H4 Preprocessing
H4 News
H4 Community
H4 Who uses scikit-learn?

Skipping heading levels breaks the document outline. Screen readers may interpret missing levels as structural errors.

Why this matters

Skipping heading levels breaks the document outline — screen-reader users lose track of section nesting.

Learn more ▾

Screen reader users navigate by jumping between headings (H1 → H2 → H3). Skipping (H1 → H3) breaks the sense of hierarchy. Use sequential levels even if you don't like the default styling — restyle with CSS instead. WCAG 1.3.1 (Info and Relationships) treats this as an A failure.

Source: WCAG 2.1 SC 1.3.1 / W3C WAI

A+

Form Accessibility

All 1 controls labeled

PASS

All 1 controls labeled

1 control(s) properly labeled

1 controls

1 labeled

0 placeholder only

0 unlabeled

Control	Type	Label	Method
q	search	Search the docs ...	aria-label

Link & Button Quality

112 links, 9 buttons — all OK

PASS

112 links, 9 buttons — all OK

3 link(s) open in new tab without warning

Add '(opens in new tab)' to link text or aria-label.

Got: https://github.com/scikit-learn/scikit-learn; https://github.com/scikit-learn/scikit-learn; https://scikit-learn.org/dev/developers/contributing.html

109 link(s) with descriptive text

112 links

0 empty

0 generic text

3 new tab

0 empty buttons

Element	Text	Issue	Suggested Fix
https://github.com/scikit-learn/scikit-l…	GitHub	new tab	Add '(opens in new tab)' to text
https://github.com/scikit-learn/scikit-l…	GitHub	new tab	Add '(opens in new tab)' to text
https://scikit-learn.org/dev/developers/…	contributing	new tab	Add '(opens in new tab)' to text
about.html#funding	scikit-learn development and m…	img no alt	Add alt attribute to the image

118 links and buttons have descriptive text

Add '(opens in new tab)' to link text or aria-label.

https://github.com/scikit-learn/scikit-learn; https://github.com/scikit-learn/scikit-learn; https://scikit-learn.org/dev/developers/contributing.html

Why this matters

Links with target="_blank" without rel="noopener" leak the originating page's window context — security and UX issue.

Learn more ▾

Without rel="noopener", the new tab can navigate the original tab via window.opener (tab-nabbing attack). Modern browsers default to noopener for target=_blank but only since recent versions. Always set rel="noopener noreferrer" explicitly.

Source: MDN target / OWASP

A+

Color Contrast (Screenshot)

20 text elements analyzed, 0 fail WCAG AA

PASS

Analyzes text contrast against the actual rendered page, including background images, gradients, and overlays that CSS-based tools cannot detect.

20 pass

Show all checked elements (20)

Element	Ratio	Required	FG	BG	Result
h1 scikit-learn	21.00:1	3.0:1	#000000	#FFFFFF	Pass
title scikit-learn: machin…	21.00:1	4.5:1	#000000	#FFFFFF	Pass
a Skip to main content	21.00:1	4.5:1	#000000	#FFFFFF	Pass
button Back to top	8.39:1	4.5:1	#000000	#38AFE1	Pass
kbd Ctrl	9.09:1	4.5:1	#000000	#4EB6E0	Pass
a Install	9.81:1	4.5:1	#000000	#65BCDF	Pass
a User Guide	10.70:1	4.5:1	#000000	#7BC3DE	Pass
a API	11.60:1	4.5:1	#000000	#91C9DD	Pass
a Examples	12.70:1	4.5:1	#000000	#A7D0DC	Pass
a Community	13.82:1	4.5:1	#000000	#BDD6DC	Pass
button More	15.14:1	4.5:1	#000000	#D3DDDB	Pass
a Getting Started	16.46:1	4.5:1	#000000	#E9E3DA	Pass
a Release History	17.82:1	4.5:1	#000000	#FDE9D8	Pass
a Glossary	17.20:1	4.5:1	#000000	#FEE4CE	Pass
a Development	16.56:1	4.5:1	#000000	#FEDFC3	Pass
a FAQ	15.84:1	4.5:1	#000000	#FED9B9	Pass
a Support	15.11:1	4.5:1	#000000	#FDD3AE	Pass
a Related Projects	14.54:1	4.5:1	#000000	#FDCEA4	Pass
a Roadmap	13.90:1	4.5:1	#000000	#FDC899	Pass
a Governance	13.34:1	4.5:1	#000000	#FCC38F	Pass

Methodology: The top 20 text elements by font size were checked. Background color was sampled from the desktop screenshot using a 5-point pattern. WCAG 2.1 AA requires 4.5:1 for normal text and 3:1 for large text.

A+

Lighthouse Accessibility Audits

Score 95/100 — 2 failing, 24 passed

PASS

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
News `div.container > div.row > div.col-md-4 > h4.sk-landing-call-header`
scikit-learn 1.9 (Changelog) `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
Changelog `div.col-md-4 > ul.sk-landing-call-list > li > a`
What's new (Changelog) `div.col-md-4 > ul.sk-landing-call-list > li > a`
What's new `ul.sk-landing-call-list > li > a > strong`
Community `div.container > div.row > div.col-md-4 > h4.sk-landing-call-header`
people `div.col-md-4 > ul.sk-landing-call-list > li > a`
contributing `div.col-md-4 > ul.sk-landing-call-list > li > a`
related projects `div.col-md-4 > ul.sk-landing-call-list > li > a`
FAQ `div.col-md-4 > ul.sk-landing-call-list > li > a`
Support `div.col-md-4 > ul.sk-landing-call-list > li > a`
Discussions `div.col-md-4 > ul.sk-landing-call-list > li > a`
Stack Overflow `div.col-md-4 > ul.sk-landing-call-list > li > a`
mailing list `div.col-md-4 > ul.sk-landing-call-list > li > a`
blog.scikit-learn.org `div.col-md-4 > ul.sk-landing-call-list > li > a`
logos and branding `div.col-md-4 > ul.sk-landing-call-list > li > a`
calendar `div.col-md-4 > ul.sk-landing-call-list > li > a`
scikit-learn central `div.col-md-4 > ul.sk-landing-call-list > li > a`
linkedin/scikit-learn `div.col-md-4 > ul.sk-landing-call-list > li > a`
bluesky/scikit-learn.org `div.col-md-4 > ul.sk-landing-call-list > li > a`
@sklearn `div.col-md-4 > ul.sk-landing-call-list > li > a`
youtube.com/scikit-learn `div.col-md-4 > ul.sk-landing-call-list > li > a`
@scikitlearnofficial `div.col-md-4 > ul.sk-landing-call-list > li > a`
@scikitlearnofficial `div.col-md-4 > ul.sk-landing-call-list > li > a`
@scikit.learn `div.col-md-4 > ul.sk-landing-call-list > li > a`
@scikit-learn `div.col-md-4 > ul.sk-landing-call-list > li > a`
our code of conduct. `div.col-md-4 > ul.sk-landing-call-list > li > a`
Who uses scikit-learn? `div.container > div.row > div.col-md-4 > h4.sk-landing-call-header`
More testimonials... `div.row > div.col-md-4 > p.sk-more-testimonials > a`

These are opportunities to improve the legibility of your content.

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
Machine Learning in Python `div.container > div.row > div.col-md-6 > h4.sk-landing-subheader`

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

●`[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

●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

●Touch targets have sufficient size and spacing.

●Skip links are focusable.

●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 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

○Form elements have associated labels

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

○`<object>` elements have alternate text

○Select elements have associated label elements.

○No element has a `[tabindex]` value greater than 0

○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.

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.