id attribute values must be unique

Log in (Premium content) Request a demo

Rule Description

The value assigned to the id="" attribute must be unique to prevent the second instance from being overlooked by assistive technology. Put another way, id attributes may not be used more than once in the same document in order to differentiate each element from another.

The Algorithm, in Simple Terms

Ensures that each element on the page with an id attribute has a unique id attribute value.

Why this is Important

The id attribute uniquely identifies elements on a page. It does not make sense to duplicate an id.

How to Fix the Problem

Rename attributes that reuse an id.

Compliance Data & User Impact

User Impact: Critical
Disabilities Affected:
  • Blindness
  • Deafblindness
Issue Type:
  • WCAG 2.0 (A): MUST
  • WCAG 2.1 (A): MUST
WCAG Success Criteria:
  • 4.1.1 Parsing
Section 508 Guidelines:
  • Not applicable

Related Deque University Course Pages

Other Related Resources

Additional Information

Relevant Technologies:
  • HTML 4
  • HTML5
Test Reliability: Automated testing is possible, with high accuracy
Rule ID: duplicate-id