HTML / XML / JS, low-level validity (cross-cutting)MediumVerified
Duplicate id attributes
An id is meant to be unique per page. Duplicates break CSS, JavaScript and accessibility references that depend on the id being singular.
What it is
Repeated ids.
Why it matters
Breaks in-page anchors and ARIA references (a11y/agents).
How to fix it
Make ids unique.
How to find it on your site
- Validate the page and look for duplicate id attributes.
- Find where the duplicates are generated.
- Make each id unique.
- Re-validate and test the dependent behaviour.
Cross-reference to ranking and citation factors
Duplicate ids break scripting, styling and accessibility links. Unique ids keep those references reliable.
Impact
Low-medium; a11y/agents. Direct (WCAG/ARIA parsing).
Evidence
Unique ids are required for valid ARIA/anchors. W3C, Web Content Accessibility Guidelines (WCAG) 2.2; W3C, WAI-ARIA Authoring Practices
Sources