When crafting the perfect URL, every character matters. One of the most long-standing debates in SEO is the choice between using hyphens (-) and underscores (_) as word separators. While it may seem like a minor detail, the impact on how search engines interpret your URLs is significant. The verdict is clear and has been confirmed by Google itself: hyphens are the superior choice for SEO.
The core of the issue lies in how search engines read and process these characters. A hyphen is treated as a space, allowing search engines to parse out individual words and understand the topic of your page. An underscore, on the other hand, is seen as a joiner, mashing words together and obscuring their meaning. This can make it much harder for your page to rank for its target keywords. For more details on creating clean URLs, see our articles on avoiding URL parameters and multiple slashes.
The Technical Divide: How Google Sees Hyphens vs. Underscores
According to Google’s official documentation, using hyphens to separate words is recommended because it helps them understand the content of the page more accurately. Let’s break it down:
- A URL with hyphens:
/red-running-shoesis interpreted by Google as “red running shoes”. - A URL with underscores:
/red_running_shoesis interpreted by Google as “redrunningshoes”.
As you can see, the hyphenated version is clearly understood, while the version with underscores becomes a single, nonsensical word to the search engine. This simple difference can have a major impact on your ability to rank for valuable, multi-word keywords.
Best Practices for URL Word Separators
For optimal SEO performance, follow these simple rules for separating words in your URLs.
| Do | Don’t |
|---|---|
| Use hyphens to separate all words in your URL slugs. | Use underscores, spaces, or any other characters to separate words. |
| Keep URLs concise, descriptive, and easy to read for users. | Mash words together without any separators. |
| If you change an old URL, implement a 301 redirect to the new one. | Leave old, underscore-using URLs to become broken links. |
Fixing Existing URLs with Underscores
If your site already has URLs that use underscores, you have a decision to make. If a page is ranking well and driving traffic, changing the URL can be risky. However, for pages that are underperforming or for all new content, you should absolutely use hyphens. If you decide to update your old URLs, make sure to use permanent 301 redirects to pass the link equity from the old URL to the new, hyphenated one. For a more in-depth look at URL best practices, check out this comprehensive guide on URL structure from Moz.
Frequently Asked Questions
Why are hyphens better than underscores in URLs for SEO?
Google’s search engine treats hyphens (-) as word separators, but does not for underscores (_). This means a URL like ‘blue-shoes’ is read as ‘blue shoes’, while ‘blue_shoes’ is read as ‘blueshoes’. Using hyphens helps Google understand the keywords and content of your page, which can lead to better rankings.
Will I be penalized for using underscores in my URLs?
While there’s no direct ‘penalty’ for using underscores, it is a missed optimization opportunity. By not separating words, you make it harder for search engines to understand your page’s topic, which can negatively impact its ability to rank for your target keywords.
Should I change all my old URLs that use underscores?
If a page with underscores is already ranking well and gets significant traffic, it might be best to leave it alone to avoid risking a drop in performance. However, for underperforming pages or all new content, you should use hyphens. If you do change old URLs, be sure to implement a permanent 301 redirect from the old URL to the new one.
Is your URL structure sending the right signals? Use Creeper to audit your URLs and ensure they are optimized for search.