Matan · WCAG · Robust
Unique IDs (WCAG)
WCAG 4.1.1 (and good HTML): id values must be unique in a document.
Pass condition in our engine: No duplicate id attributes on the page.
This WCAG check is part of SEO-GEO scoring 2.2.1, last updated 2026-09-18. About 90 percent of the evaluation runs on the HTML we crawl, so you can verify the same pass condition with a free report.
1. Problem description
Duplicate ids break label for=, aria-labelledby, skip links and fragment navigation. They often come from repeating a widget without namespacing ids.
2. Most common causes
- A slider partial included three times with id="slide".
- Server-rendered lists using a constant id.
3. How to fix it
- Generate unique ids (include an index or entity id).
- Prefer classes for styling, ids only when you must target one node.
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