Technical Reference

What Lumi checks

58 proprietary rules across five engines, plus axe-core and HTML_CodeSniffer. Every check mapped to WCAG criteria.

350+

Total rules

Proprietary rules

Unique to Lumi

Advisoryrules are best-practice checks we surface for action but exclude from your accessibility score, so a passing site is never penalised for a judgement call.

Lumi Custom Checks

58 DOM rules that catch issues axe-core and WAVE miss.

Heading Structure

(3)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
More than one <h1> on the page lumi-multiple-h1 Advisory	2.4.6 (AA)	Moderate
Heading level skipped (e.g. h2 → h4) lumi-heading-skip	1.3.1 (A)	Moderate
Heading element with no text content lumi-empty-heading	2.4.6 (AA)	Moderate

Link Quality

(1)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Generic link text ('click here', 'read more') with no aria label lumi-generic-link-text	2.4.4 (A)	Serious

Alt Text Quality

(5)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Alt text that looks like a filename or placeholder lumi-suspicious-alt-text	1.1.1 (A)	Serious
Alt text under 5 characters lumi-alt-too-short Advisory	1.1.1 (A)	Moderate
Alt text over 200 characters lumi-alt-too-long Advisory	1.1.1 (A)	Minor
Alt text duplicates nearby visible text lumi-alt-redundant Advisory	1.1.1 (A)	Moderate
Three or more images share identical alt text lumi-duplicate-alt-text Advisory	1.1.1 (A)	Moderate

Language

(1)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Invalid html lang code lumi-invalid-lang	3.1.1 (A)	Serious

Landmarks & Page Structure

(7)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Two or more navs, one without an accessible label lumi-nav-without-label	2.4.1 (A)	Moderate
Page has no <main> landmark lumi-missing-main	2.4.1 (A)	Serious
Significant content (40+ chars) outside any landmark lumi-content-outside-landmark Advisory	1.3.1 (A)	Moderate
Page has no <header>/banner landmark lumi-missing-header UniqueAdvisory	1.3.1 (A)	Moderate
Search field not inside a search landmark lumi-missing-search-landmark UniqueAdvisory	1.3.1 (A)	Moderate
Duplicate landmarks, one unlabelled lumi-duplicate-landmark-no-label Unique	1.3.1 (A)	Moderate
<main> nested inside aside/nav lumi-landmark-nesting Unique	1.3.1 (A)	Serious

Non-Text Contrast

(3)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Button border/background under 3:1 against adjacent background lumi-button-contrast UniqueAdvisory	1.4.11 (AA)	Serious
Form field border under 3:1 against background lumi-input-contrast UniqueAdvisory	1.4.11 (AA)	Serious
Custom checkbox/radio border under 3:1 lumi-custom-checkbox-contrast UniqueAdvisory	1.4.11 (AA)	Serious

ARIA Validation

(8)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
aria-label is empty or whitespace lumi-empty-aria-label	4.1.2 (A)	Serious
aria-labelledby/describedby points to a missing id lumi-broken-aria-reference	4.1.2 (A)	Serious
Invalid aria-live value lumi-aria-live-invalid	4.1.3 (AA)	Serious
role=alert/status combined with aria-live=off lumi-aria-live-conflict	4.1.3 (AA)	Serious
Abstract ARIA role used in markup lumi-abstract-role Unique	4.1.2 (A)	Serious
Role duplicates an element's implicit semantics lumi-redundant-role Unique	4.1.2 (A)	Minor
Interactive role with no tabindex lumi-interactive-role-not-focusable Unique	4.1.2 (A)	Serious
div/span role=button without tabindex lumi-div-button-no-keyboard Unique	4.1.2 (A)	Critical

Forms & Input

(7)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Personal-data field with no autocomplete attribute lumi-missing-autocomplete Advisory	1.3.5 (AA)	Moderate
Field with no programmatic label lumi-label-not-associated Advisory	1.3.1 (A)	Serious
'*'/required text but no required/aria-required lumi-required-not-programmatic Advisory	3.3.1 (A)	Serious
Red border with no text/ARIA error indication lumi-colour-only-error Advisory	1.4.1 (A)	Serious
Password field blocks paste (breaks password managers) lumi-paste-blocked	3.3.8 (AA)	Serious
Password field missing autocomplete attribute lumi-auth-autocomplete Advisory	3.3.8 (AA)	Moderate
CAPTCHA with no accessible alternative lumi-captcha-no-alt Advisory	3.3.8 (AA)	Critical

Tables

(4)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Data table with no <th> header cells lumi-table-no-headers	1.3.1 (A)	Serious
Header cells missing scope attributes lumi-table-missing-scope Advisory	1.3.1 (A)	Moderate
Table with no caption or accessible label lumi-table-no-caption Advisory	1.3.1 (A)	Moderate
Rows with inconsistent column counts lumi-table-broken-structure	1.3.1 (A)	Moderate

Media, Motion & Other

(5)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Interactive element under 24×24px lumi-small-touch-target Advisory	2.5.8 (AA)	Moderate
Animates despite prefers-reduced-motion lumi-no-reduced-motion Advisory	2.3.3 (AAA)	Moderate
Autoplaying media that is not muted lumi-autoplay-media	1.4.2 (A)	Serious
outline:none with no focus fallback lumi-outline-removed Advisory	2.4.7 (AA)	Serious
Viewport blocks zoom (user-scalable=no) lumi-zoom-disabled	1.4.4 (AA)	Critical

Structure Advisor

(3)

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Nav with 3+ links but no <ul> lumi-structure-nav-without-list UniqueAdvisory	1.3.1 (A)	Minor
<main> contains no heading lumi-structure-heading-landmark-mismatch UniqueAdvisory	1.3.1 (A)	Minor
Landmarks not in conventional order lumi-structure-landmark-order UniqueAdvisory	1.3.1 (A)	Minor

Keyboard Interaction Tests

7 real-browser tests using Playwright. Most scanners analyse the DOM only - Lumi actually tabs through the page and tests keyboard navigation.

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Focused element hidden by a sticky/fixed bar lumi-focus-obscured UniqueAdvisory	2.4.11 (AA)	Serious
Tab gets stuck with no escape keyboard-trap Unique	2.1.2 (A)	Critical
No visible focus indicator on a focused element focus-visible Unique	2.4.7 (AA)	Serious
No skip-navigation link found skip-link UniqueAdvisory	2.4.1 (A)	Moderate
Skip link points to a missing id skip-link-target Unique	2.4.1 (A)	Serious
onclick/role element with no tabindex keyboard-accessible UniqueAdvisory	2.1.1 (A)	Critical
Focus order doesn't match visual layout tab-order UniqueAdvisory	2.4.3 (A)	Moderate

AI-Powered Checks

Computed visual analysis that detects issues requiring understanding of how elements actually render - not just what the HTML says.

Accessibility rules and their WCAG criteria
Rule	WCAG	Impact
Text placed over a background image/gradient lumi-ai-contrast-bgimage UniqueAdvisory	1.4.3 (AA)	Serious
Text cut off by ellipsis/line-clamp lumi-ai-text-truncated UniqueAdvisory	1.3.1 (A)	Moderate
Icon button with no accessible label lumi-ai-icon-only-button UniqueAdvisory	4.1.2 (A)	Serious
Colour used as the only indicator of meaning (status dots etc.) lumi-ai-colour-only UniqueAdvisory	1.4.1 (A)	Serious
Claude screenshot review (premium Deep Scan); human-reviewed before the client sees it lumi-ai-deep UniqueAdvisoryDeep Scan	Best practice	Moderate

Third-Party Engines

Every scan also runs axe-core (~84 rules, industry standard) and HTML_CodeSniffer (WCAG 2AA standard). Results are deduplicated across all engines so each issue is reported once with the most detailed information from whichever engine found it.

Legend

UniqueNot checked by axe-core, WAVE, or Lighthouse

AdvisoryBest practice, excluded from score

CriticalBlocks access entirely

SeriousMajor barrier

ModerateCauses difficulty

MinorBest practice