What is `ff.im`?

When we visit fm.im, we are r开发者_StackOverflowedirected to http://friendfeed.com.

Here are some other examples:

1. ff.im/abc
2. ff.im/efg

How is FriendFeed able to do this?

.im is the Isle of Man top-level domain (ccTLD). The registry normally requires names to be at least three characters long, unless you pay considerably more.

Two-character domains look cool but aren't particularly useful since IE rejects their cookies (old article, but still mostly true for newer IE versions).

When your browser requests ff.im:

GET / HTTP/1.1
host: ff.im

their webserver responds with a redirect, either to the main FriendFeed site:

HTTP/1.1 302 Found
Date: Sat, 09 Apr 2011 12:29:38 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
Content-Length: 0
Location: http://friendfeed.com/
Server: FriendFeedServer/0.1

or to some other place (when using their URL-shortener).