The difference between URL, URI and URN

I have recently figured out what the difference between URI and URL is. It turns out that URI is more general, because it introduces URNs.
| posted on Mon, 07 Feb 2005, 13:53 | weblog | rss | spin-off | comments |

The idea is that a URL is a mechanical link to a resource's location, where it can be downloaded. For this reason, a URL contains a hostname and a local part, all of which can be resolved anywhere on the Internet.

What a URN tries to do is different. It tries to give a description of a resource without actually pointing at it. For example:


This is the URN for my PhD thesis, but it does not give you a clue where you could get it. The idea is that you need resolution software to come to that. The word isbn is a so-called URN-space, and it has been registered formally. There are also non-global URN spaces, they start with an x- prefix.

URI is merely the possibly overlapping union of strings that are a URL or a URN.

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