Home page > Scripts > HowTo: Expand Short URLs

HowTo: Expand Short URLs

Saturday 9 January 2010, by Fil

All the versions of this article: [English] [français]

Short URLs have been plaguing the Web. They break links, enable surfing surveillance, forbid us to know if we have visited such or such article before, and remove any indication of what’s behind your next click.

With long.rezo.net, you can now dereference those short URLs, and peek at the address they point to without actually going to it.

PNG - 180.5 kb
Screenshot of the long.rezo.net website

In the “short url” input enter your short URL, and the site will indicate its destination address, with a link to it in case you want to proceed.

Bonus : your (long) address is checked on delicious and you will see its title and associated tags if it has already been registered.

How it works

The script that dereferences a short URL is a simple application of the HTTP protocol. The site calls the short URL, and checks if the headers contain a redirection line Location: long address.

In PHP this is done with the following code:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false);
$a = curl_exec($ch);
if(preg_match('#Location: (.*)#', $a, $r))
 $l = trim($r[1]);

Going a bit further

I tried to find a method to go a bit further, because copy-pasting the short URL on the long.rezo.net website is not very convenient. To do it systematically, I toyed with my computer’s configuration.

In the HOSTS file (help) I’ve added the following line:

Then any call to one of those short URLs system is routed to my server at IP address, on which I’ve configured a simple mechanism to intercept those URLs, and proxy the others to their (legitimate) destination.

Her’s my apache configuration for these services:

Maybe a bit complex to install, this method enables me to get the long.rezo.net URL each time I click on a short URL, anywhere on my computer — in my email, in my twitter client, and so on.

You can use if you wish to test, but I encourage you to install your own proxy, as my system is very much experimental.

If you have a better idea to do this, please indicate it in the forum below!