Opportunity Technical SEO
URL contains underscores
- Severity
- Opportunity
- Impact
- Low
- Effort to fix
- Medium
- Issue code
url_underscore
Why it matters
Search engines treat hyphens as word separators but not underscores, so words run together.
How to fix it
Use hyphens instead of underscores in new URLs.
What this means
The URL's path contains underscores, for example /running_shoes_guide. Google recommends hyphens to separate words in URLs: /running-shoes-guide.
Why it matters
Google's guidance is that hyphens help it and people see the separate words in a URL. Underscores can make running_shoes read as one token. The effect on rankings is small, and Google has said it is not worth changing an established site's URLs only for this.
That makes this a low-priority opportunity:
- New pages and new sections: use hyphens from the start.
- Existing pages: change them only as part of a larger URL restructure or migration, where redirects are being set up anyway.
Common causes
- File-based sites where page names came from file names, such as
about_us.html. - CMS slugs generated from database field names or product codes.
- Frameworks that default to underscores in route names.
How to fix it
- Change the slug setting or naming convention so new URLs use hyphens.
- If you do rename existing URLs, add a 301 redirect from each old URL to the new one, and update internal links, canonical tags and the XML sitemap in the same release.
- Leave underscores in technical paths that visitors never see in search results, such as
/wp_content/style asset folders.
Verify the fix
Recrawl. Renamed URLs show as Redirecting URL until every internal link points to the new address; Links to redirecting internal URLs lists the ones left to update.
How it affects your score
Finding this issue on any page costs the Technical SEO score 0.5 points, plus up to 4 more depending on the share of crawled pages affected. A smaller improvement with a modest effect on its own.
Find the affected URLs
Open Crawl > Issues and pick URL contains underscores. Each affected URL is listed with its evidence, and Copy URLs or Export URLs hands the list to a developer. The issue also appears in the Action Plan, ranked by impact (low) and effort (medium), and in the issues CSV under the code url_underscore. After fixing, run a new audit and use Compare to confirm the URLs moved to fixed.