URL Has Underscore

Element Code: UR-006

What this check flags

This check scans your URL paths for the underscore character, as in /blog/best_running_shoes instead of /blog/best-running-shoes. It is purely about the word-separator character inside the path or slug. It is not about query string parameters, and it is not about underscores that appear inside a single meaningful token like a product SKU or filename where there is no word boundary to separate in the first place.

This is one of the oldest, most specific pieces of URL guidance Google has ever published, and it has not changed. Google's own SEO documentation states plainly that hyphens should be used to separate words in a URL. The reason is mechanical: Google's URL parser treats a hyphen as whitespace between words, so best-running-shoes is parsed as the three words "best," "running," "shoes." An underscore is treated as a literal character that joins the strings together, so best_running_shoes risks being parsed closer to "bestrunningshoes" as far as keyword matching is concerned.

Why this matters, and why it is a small deal

I will be straight with you: this is not going to move your rankings on its own in any way you could measure with a before-and-after test. If your content, links, and relevance are strong, an underscore in a URL is not what is holding you back. But it is one of the few pure SEO recommendations that costs you literally nothing to follow correctly on new pages, and correcting it does have a real, if marginal, benefit for how cleanly your target keywords get parsed out of the URL string.

There is a secondary, more human reason to fix it: readability and click confidence. A hyphenated URL displayed in search results or shared as a link reads naturally, word by word. An underscored URL looks slightly technical and dated, and on some fonts and in some browser address bars underscores render as barely visible or get confused with spaces, especially when a link is underlined. Hyphens do not have that problem. This is a small trust and usability signal on top of the small technical one.

Where this stops being a shrug-worthy nitpick is at scale. If your CMS defaults to underscores and you have thousands of URLs built that way, you are accumulating thousands of small missed opportunities for exact keyword matching in the URL, plus thousands of slightly less clickable links in the SERP. Fix the template, not just one URL, or you will keep generating the same problem on every new page.

How to detect underscored URLs at scale

• Screaming Frog: crawl the site, export the URL list, and filter for the underscore character in Excel or Google Sheets. This gives you a full inventory in minutes.
• Sitebulb: its URL Standardisation audit section flags non-hyphenated separators as part of its default checks.
• Google Search Console: check the Pages report and the Performance report's Pages filter for any URL patterns containing underscores to see how many are indexed and getting traffic today, which tells you what you cannot break with a careless redirect.
• Sitemap review: grep your XML sitemap for underscore characters as a quick sanity check before or after a migration.
• Server logs: if you are mid-migration, check log files to confirm bots and users are actually being redirected from old underscored URLs, not hitting soft 404s.

How to fix it, step by step

1. Inventory every URL with an underscore using a full site crawl, not a sample. You need the complete list before you touch redirects.
2. Decide on the hyphenated equivalent for each URL, keeping the rest of the path structure identical, only the separator changes.
3. Set up 301 redirects from every old underscored URL to its new hyphenated version. This step is not optional, changing a live, indexed URL without a redirect throws away its rankings and any backlinks pointing at it.
4. Update all internal links, navigation, sitemaps, and canonical tags to point directly at the new hyphenated URLs, do not rely on the redirect chain internally.
5. Fix the root cause in your CMS or URL-generation logic so newly created pages default to hyphens, otherwise you will be back here in six months with a fresh batch of underscored URLs.
6. Re-crawl after deployment to confirm old URLs 301 cleanly to the new ones with no redirect chains or loops, and that the new URLs return 200.

How Google parses the separator

/best-running-shoes parsed as best + running + shoes hyphen = word separator

Fix flow: crawl for underscores → map to hyphenated URLs → 301 redirect old to new → update internal links and sitemap → fix CMS default so new URLs never regress Skip the redirect step and you lose rankings and links, not gain them.

Underscore vs hyphen, side by side

FAQ