Google’s Matt Cutts released a new video addressing the hyphen vs underscore for URLs. This isn’t the first time that Cutts has discussed this issue, but the last video on the topic is years old and the time seemed right for an update.
In the video Matt Cutts once again reaffirms what we’ve known all along: you should use dashes for SEO URLs, and not underscores.
Google treats underscores as word joiners, while it treats hyphens as word seperators. In other words the hyphen is like having a space between the words and tells Google and that they should be treated as two separate words. We know that using keywords in your URL can have a very significant ranking impact, but does it really matter whether they’re separated with dashes or underscores? In the video Cutts said:
“In practical terms it doesn’t make that much of a difference. It’s what we call a secondary effect; it’s not a primary thing that really makes a huge difference.”
In other words the difference is small, but the difference is there. So dashes could make you rank better, a little bit, maybe (depending on the state of your competition, of course — if you’re miles away from the next highest ranker, dashes aren’t going to help).
Overall Cutts recommends that you should not rewrite all of your URLs if you’re currently using underscores, but if you’re making new pages or a new site, you should use hyphens:
“If you are going to make a site and you’re starting fresh — so you’ve got a blank slate to work with — I would probably go ahead and go with dashes. I would continue to go with dashes at least for the foreseeable future.”
“Nobody’s slated to be working on that so at least for the time being it’s better to use the dash.”
Here’s the full video, where Cutts also discusses some of the history of the underscore, why they use it as a jonier instead of a separator, and why it’s not high on their priority list to change.