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Using Dashes & Underscores in URLs: SEO-friendly Approach & Results
Explore an in-depth comparison of using dashes or underscores in URLs for SEO optimization. Gain insights on their impact on search results, tips for webmasters, and best practices.

The Ongoing Debate: Dashes vs. Underscores in Your Site’s URL for SEO

When building a new site from the ground up or optimizing an existing one, webmasters encounter a myriad of decisions regarding various minutiae in SEO. Among these decisions, the choice between using dashes and underscores in URL structures is often overlooked. Many website owners wonder why such a seemingly insignificant detail matters in SEO. The answer is straightforward: Google interprets dashes and underscores differently.

Underscores as Joiners, Dashes as Separators

Google considers underscores as connectors between two keywords, while a dash (or hyphen) indicates a separation of the keywords. For instance, to Google, "blue_shoes" is perceived as one term: "blue_shoes". However, Google interprets "blue-shoes" as two distinct keywords: "blue" and "shoes". Consequently, if your URL contains "blue_shoes", Google will only serve that page if the user searches for "blue_shoes"—a less likely scenario. If your URL contains "blue-shoes", that page can potentially appear in the search results for "blue", "shoes", and "blue shoes". According to Google's former head of webspam, Matt Cutts, this distinction between punctuation originates from Google's early days when its engineers—being primarily computer programmers—wanted to easily locate specific terms within the code. The practice has since carried over and evolved with Google’s search algorithm. Treating underscores as joiners is still a part of Google's latest updates as of my knowledge cutoff in September 2021, and there hasn't been any indication of changing this interpretation.

The Real Impact on Search Results

While there is a significant difference between how the two punctuation marks are treated, Matt Cutts suggested that using dashes instead of underscores in URLs "doesn’t make that much of a difference" in relation to Google search results. It is a "second order effect" rather than a primary one. Take Wikipedia as an example: the website encompasses millions of URLs that contain only underscores, not dashes. However, this does not affect Wikipedia’s ranking as there are numerous other signals Google considers when determining SERPs. Apart from Google, as of my last update in September 2021, Microsoft's search engine Bing does not distinguish between underscores and dashes—they are both seen as separators.

Advice for Webmasters

If your website already utilizes underscores in its URL structures, and it ranks well due to other factors, it may not be worth the time and effort to rewrite all of them to include hyphens and create 301 redirects. Altering all of your website’s URLs could potentially create more problems than merely sticking with the underscores. However, if you're starting a new website and have yet to establish your presence in search rankings, it's advisable to use dashes between keywords in your URLs. From a user's perspective, dashes offer greater visibility and usability. Underscores can get hidden by the link itself and appear as spaces, potentially confusing visitors. Consider these two URLs:


The underscore disappears into the underlined text, making it difficult for users to decipher the real URL and possibly link back to the website.

Our Perspective

Based on Google's stance, dashes do hold an edge over underscores as the preferred URL punctuation. While this does have an impact, it's also important to consider other SEO factors. Even for established websites, it might be worth considering a rewrite of your top-performing pages' URLs if they use underscores. Google has shown a clear preference for the dash.

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