How does Google find keywords in the URL?

Take the following 4 URLs (I'm also assuming you read the previous article about how you construct your links too):

* example.com/seoforaspnetdevelopers/
* example.com/SeoForAspnetDevelopers/
* example.com/seo_for_aspnet_developers/
* example.com/seo-for-aspnet-developers/

There are 4 total keywords 'seo', 'for', 'aspnet', and 'developers'.

Which format is better? Or does it really even matter? Hopefully it comes as no surprise that the first 2 examples are virtually identical and in neither case, from what my research has shown, does Google use any casing information to pull out keywords. So the first 2 examples are very bad choices for how to format your URL if you care about SEO. In the 3rd example underscores are used to breakup the keywords and in the 4th example dashes are used.

Google has stated that the preferred way to break-up keywords in the URL is to use dashes. Most modern content management systems and blog engines use this as the preferred method.