Hyphen, underscore, or camelCase as word delimiter in URIs?

You should use hyphens in a crawlable web application URL. Why? Because the hyphen separates words (so that a search engine can index the individual words), and a hyphen is not a word character. Underscore is a word character, meaning it should be considered part of a word.

Double-click this in Chrome: camelCase
Double-click this in Chrome: under_score
Double-click this in Chrome: hyphen-ated

See how Chrome (I hear Google makes a search engine too) only thinks one of those is two words?

camelCase and underscore also require the user to use the shift key, whereas hyphenated does not.

So if you should use hyphens in a crawlable web application, why would you bother doing something different in an intranet application? One less thing to remember.

The standard best practice for REST APIs is to have a hyphen, not camelcase or underscores.

This comes from Mark Masse's "REST API Design Rulebook" from Oreilly.

In addition, note that Stack Overflow itself uses hyphens in the URL: .../hyphen-underscore-or-camelcase-as-word-delimiter-in-uris

As does WordPress: http://inventwithpython.com/blog/2012/03/18/how-much-math-do-i-need-to-know-to-program-not-that-much-actually