- Class
- C2 Recommended
- Weight
- 4
- Severity on fail
- major
- Applies to
Scope and evidence
Evaluated on each member of I. The book marks this requirement DOCUMENTED RECOMMENDATION, SEARCH-ENGINE-SPECIFIC.
The reason must not claim a ranking effect. The second citation is included so readers can weigh the cost of changing existing URLs.
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.
underscore_in_pathThe path of {url} separates words with underscores. Google recommends hyphens instead of underscores to separate words in URLs.
The documented fix
Use hyphens in slugs for new URLs. For existing URLs, weigh the change carefully and, if you make it, add a permanent redirect from every old URL.
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.
“we recommend using hyphens (-) instead of underscores (_) to separate words in your URLs”
[G-URL] URL structure best practices for Google Search · Use hyphens to separate words · last updated 2025-12-10
https://developers.google.com/search/docs/crawling-indexing/url-structure“alone have hardly any effect beyond appearing in breadcrumbs”
[G-STARTER] Search Engine Optimization (SEO) Starter Guide · Things we believe you shouldn't focus on · last updated 2025-12-10
https://developers.google.com/search/docs/fundamentals/seo-starter-guide