Accessibility

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

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Checks

4 PASS 3 REVIEW 6 FIX

Landmark Structure

Action

5 landmarks

FIX

5 landmarks

No <main> landmark found

Screen reader users cannot quickly navigate to the primary content. Wrap your main content in <main>.

3 <nav> landmark(s) found

2 of 3 <nav> elements are unlabeled

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

No contentinfo (footer) landmark

Skip navigation link is missing (WCAG 2.4.1)

Add a skip link as the first focusable element so keyboard users can bypass repeated navigation.

Page Structure — as a screen reader sees it

Screen reader users cannot quickly navigate to the primary content. Wrap your main content in <main>.

Why this matters

Without a <main> landmark, screen-reader users can't skip past the navigation to the page content — every page starts with re-reading the menu.

Learn more ▾

The <main> element marks the page's primary content area. Assistive tech offers a 'jump to main' shortcut — but only if <main> exists. Without it, every page navigation forces re-reading the header. Wrap your primary content in a single <main>.

Source: WAI-ARIA / WCAG 2.4.1

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

Add a skip link as the first focusable element so keyboard users can bypass repeated navigation.

Why this matters

Without a skip-nav link, keyboard users tab through every nav item before reaching content — every page, every visit.

Learn more ▾

WCAG 2.4.1 (Bypass Blocks) requires a mechanism to skip past repeated content. The standard implementation is a 'Skip to main content' link that's the first focusable element, visually hidden until focused. Three lines of HTML + four of CSS.

Source: WCAG 2.1 SC 2.4.1

Favicon & Branding

Action

2 icon(s) detected

FIX

2 icon(s) detected

favicon.ico present at site root

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 Present

✓ 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 ✗

Navigation UX

Action

No navigation patterns

FIX

No navigation patterns

3 navigation landmark(s) detected

No breadcrumbs, search, or skip link detected

These navigation aids help users orient themselves and find content efficiently, especially on large sites.

Breadcrumbs

Skip Link

Labeled Navigation 3 <nav> element(s)

Hamburger Menu

Sticky Navigation Cannot reliably detect (CSS-based)

1 of 6 testable patterns navigation patterns detected. Limited navigation support. Consider adding breadcrumbs, search, and skip link.

Link & Button Quality

Action

81 links, 4 buttons — all OK

REVIEW

81 links, 4 buttons — all OK

6 image-only link(s) without alt text

Image-only links need alt text on the image (or aria-label on the link) so screen readers can announce them.

Got: a#home_submit; a#home_download; a#home_learn; a#home_develop; a#home_analyze; a#home_research

4 link(s) open in new tab without warning

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

Got: https://twitter.com/NLM_NIH; https://www.facebook.com/nationallibraryofmedicine; https://www.youtube.com/user/NLMNIH; https://www.google.com/maps/place/8600+Rockville+Pike,+Bethesda,+MD+20894/@38…

71 link(s) with descriptive text

81 links

0 empty

0 generic text

4 new tab

0 empty buttons

Element	Text	Issue	Suggested Fix
https://submit.ncbi.nlm.nih.gov/	Submit …	img no alt	Add alt attribute to the image
home/download/	Download …	img no alt	Add alt attribute to the image
home/learn/	Learn …	img no alt	Add alt attribute to the image
home/develop/	Develop …	img no alt	Add alt attribute to the image
home/analyze/	Analyze …	img no alt	Add alt attribute to the image
/research/	Research …	img no alt	Add alt attribute to the image
https://twitter.com/NLM_NIH	Twitter	new tab	Add '(opens in new tab)' to text
https://www.facebook.com/nationallibrary…	Facebook	new tab	Add '(opens in new tab)' to text
https://www.youtube.com/user/NLMNIH	Youtube	new tab	Add '(opens in new tab)' to text
https://www.google.com/maps/place/8600+R…	8600 Rockville Pike Bet…	new tab	Add '(opens in new tab)' to text

75 links and buttons have descriptive text

Image-only links need alt text on the image (or aria-label on the link) so screen readers can announce them.

a#home_submit; a#home_download; a#home_learn; a#home_develop; a#home_analyze; a#home_research

Why this matters

Image-only links with no alt are unidentifiable to screen-reader users — link's destination is invisible.

Source: WCAG 2.1 SC 2.4.4

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

https://twitter.com/NLM_NIH; https://www.facebook.com/nationallibraryofmedicine; https://www.youtube.com/user/NLMNIH; https://www.google.com/maps/place/8600+Rockville+Pike,+Bethesda,+MD+20894/@38…

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

404 Error Page

Action

HTTP 404, custom page

REVIEW

HTTP 404, custom page

Correct 404 status code returned

Got: HTTP 404

Custom styled 404 page

Homepage link present on 404 page

404 Page Quality ✓ Custom 404 Page

Status Code HTTP 404 ✓Page Title 404 Error - NCBI ✓Custom Styling ✓Navigation ✗Homepage Link ✓Search Form ✗

Color Contrast (Screenshot)

Action

20 text elements analyzed, 4 fail WCAG AA

REVIEW

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

16 pass 4 fail WCAG AA

span Here's how you know

2.73:1

#000000

#20558A

needs 4.5:1 (normal text)

16px · top of page (header area)

strong The .gov means it's official.

2.73:1

#000000

#20558A

needs 3.0:1 (large text)

16px · top of page (header area)

p Federal government websites often end in…

2.73:1

#000000

#20558A

needs 4.5:1 (normal text)

16px · above the fold

a Log in

2.60:1

#000000

#505050

needs 4.5:1 (normal text)

16px · above the fold · over background image/gradient

1 contrast failures on background images/gradients

These failures are invisible to CSS-based accessibility tools like Lighthouse. The text may be fine on a solid background, but fails when rendered over an image or gradient.

Show all checked elements (20)

Element	Ratio	Required	FG	BG	Result
h1 Welcome to NCBI	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 National Center for …	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Submit	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Download	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Learn	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Develop	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Analyze	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h2 Research	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h3 Popular Resources	21.00:1	3.0:1	#000000	#FFFFFF	Pass
h3 NCBI News & Blog	21.00:1	3.0:1	#000000	#FFFFFF	Pass
title National Center for …	18.59:1	4.5:1	#000000	#F1F1F1	Pass
p An official website …	18.59:1	4.5:1	#000000	#F1F1F1	Pass
span Here's how you know	2.73:1	4.5:1	#000000	#20558A	Fail
strong The .gov means it's …	2.73:1	3.0:1	#000000	#20558A	Fail
p Federal government w…	2.73:1	4.5:1	#000000	#20558A	Fail
strong The site is secure.	11.18:1	3.0:1	#000000	#BDBDBD	Pass
p The	16.83:1	4.5:1	#000000	#E6E6E6	Pass
strong https://	17.94:1	3.0:1	#000000	#EDEDED	Pass
p ensures that you are…	7.37:1	4.5:1	#000000	#999999	Pass
a Log in	2.60:1	4.5:1	#000000	#505050	Fail

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.

Heading Hierarchy

12 headings

PASS

12 headings

Multiple H1 headings (2 found)

A page should have only one H1. Multiple H1s dilute the document outline.

H4 Account
H1 NCBI
H2 National Center for Biotechnology Information
H1 Welcome to NCBI duplicate H1
H2 Submit
H2 Download
H2 Learn
H2 Develop
H2 Analyze
H2 Research
H3 Popular Resources
H3 NCBI News & Blog

A page should have only one H1. Multiple H1s dilute the document outline.

Why this matters

Multiple H1s blur the page's primary topic — screen-reader users and Google both prefer one H1.

Learn more ▾

HTML5's outline algorithm technically allows multiple H1s within sectioning content, but no browser implements it. In practice: one H1 per page. Use H2-H6 for subsections.

Source: WCAG 2.4.6 / Google Search Central

A+

Alt Text Quality

All 11 images OK

PASS

All 11 images OK

6 decorative image(s) correctly marked

5 image(s) with good alt text

11 images 5 good alt text 6 decorative

All images have appropriate alt text.

A+

Form Accessibility

All 2 controls labeled

PASS

All 2 controls labeled

2 control(s) properly labeled

2 controls

2 labeled

0 placeholder only

0 unlabeled

Control	Type	Label	Method
#database	select	Search database	for/id
#term	text	Search term	for/id

Lighthouse Accessibility Audits

Score 91/100 — 3 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
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.

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