Stack Overflow, urls how do they work??, do they redirect? [duplicate]

This question already has answers here: 开发者_如何转开发 Closed 11 years ago.

Possible Duplicate:

Stack Overflow Question Routing

before you jump out... i know questions about stackoverflow urls have been asked 1231234123123123 times. i know because i read all of them.

this question is different, i know how they work, almost

there are one thing that i dont know EXACTLY what they did.

1. when i change the "pretty" this-is-a-nice-question to bla-bla it changes back to the original question name.

how did they do that do they change this part to the original? is it redirect? one thing im sure of is that they dont do that on the client side.

---

It's a redirect.

> wget http://stackoverflow.com/questions/7459811/stack-overflow-urls-how-do-they
...
HTTP request sent, awaiting response... 301 Moved Permanently
Location: /questions/7459811/stack-overflow-urls-how-do-they-work-do-they-redirect [following]