- Class
- C2 Recommended
- Weight
- 4
- Severity on fail
- major
- Applies to
Scope and evidence
Evaluated on site. The book marks this requirement SEARCH-ENGINE-SPECIFIC.
Fail conditions
Each condition has a stable code and a reason template. The evaluator fills the placeholders from observed values only; no sentence in a report is generated.
case_duplicates{urls} differ only in letter case, each returns 200, and they do not agree on one canonical. Google's URL handling is case sensitive, so it treats them as different URLs. Google recommends linking within your site to the canonical URL rather than a duplicate.
The documented fix
Redirect case variants to one form, or have all variants declare the same canonical; generate internal links in a single case.
Sources, quoted
These are the passages the rule rests on, stored once in the knowledge base and emitted exactly as written. A citation marked for specific conditions appears only on findings with those codes.
“is case sensitive”
[G-URL] URL structure best practices for Google Search · Be aware that URLs are case sensitive · last updated 2025-12-10
https://developers.google.com/search/docs/crawling-indexing/url-structure“When linking within your site, link to the canonical URL rather than a duplicate URL.”
[G-CANON] How to specify a canonical URL with rel="canonical" and other methods · General canonicalization best practices · last updated 2026-07-10
https://developers.google.com/search/docs/crawling-indexing/consolidate-duplicate-urls