Rule library Markup integrity

IDs used in ARIA and labels must be unique

duplicate-id-ariaWCAG 2.0 A

Ensure every id attribute value used in ARIA and in labels is unique

Who this affects

Two elements share an ID that ARIA references, so the association points at the wrong element.

How to fix it

Make every ID unique on the page.

Effort Low · ~15 min

Where this sits in the standard

WCAG success criterionLevelEN 301 549 clause
4.1.2 Name, Role, ValueA301-549, 9.4.1.2

EN 301 549 clause 9 applies these criteria to web content. The published version referenced by the European Accessibility Act is V3.2.1, which incorporates WCAG 2.1 level A and AA. More on the standard.

How to check it by hand

Run the page through an HTML validator and look specifically for duplicate id values. Duplicates break every attribute that points at an id — labels, descriptions, controls.

Automated testing settles roughly a third of the WCAG success criteria. This rule is one an automated tool detects reliably — but a clean automated result is not proof of conformance.

Reference

Deque's technical write-up for this rule: duplicate-id-aria

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