URL rewriting takes variable-based URLs (e.g., www.domain.com?id=3) and converts them to human text-based URLs (e.g., www.domain.com/hello-world.html). It helps SEO and it makes a page easier to reference. The debate: which to use, underscores or dashes?

The question of dashes versus underscores has been answered, by Matt Cutts of Google.

First, I recommend to anyone interested in SEO, that they frequent Matt's blog and continually keep up-to-date with the latest trends in search engine optimization - SEO is always evolving. To summarize Matt's blog post on dashes versus underscores - use dashes. Yup, that's it. You can read his blog for the reasoning why - it's a rather geeky exploration of the brilliant and programmatic minds behind Google's search engine algorithms. But at the end of the day, if your question is, 'should I use dashes or underscores in my URL rewrite?' - he's answered, and it's dashes.

 

Sure, in the comments on his blog, you can read some SEO guys arguing that it's not that important; that if the page uses good SEO principles then the dashes versus underscores is moot - and OK, you can argue this. But if you're employing URL rewrites as an arrow in your quiver of SEO - then do it the way he says. Since let's face it, Google is the target for most SEO - here's a guy from Google who's moving the target closer to you.

So why does the second half of my blog title imply I don't want to know this?

Well I do want to know this. In fact, it's been a subject of debate around the office - and probably will remain so for some time (even though the question has been answered as far as I'm concerned). The real pain of discovering this "old" Matt Cutt blog post - we used a mix of underscores and dashes on our own site. And well, when we discovered and read this....we had to "tweak" the programming on our site and update all our data so that our URLs use dashes. That's not hard. What's going to be hard is watching our ranking and inbound traffic fall temporarily as our old underscore-based links are scrubbed from Google and replaced with the newly updated hyphen-based URLs.

 

It'll probably take a few days to a few weeks. But eventually it'll work itself out. But that's why I wrote, you sometimes learn things you would rather not know. And even though I would agree that URL rewrites are only one item on a long list of SEO fundamentals - we did use it on our site to boost our SEO and make things more human oriented. And it's why we're willing to change our mix of underscores and dashes to all dashes - and suffer the consequences. You live and learn.