How to detect FB profile from image URL?

UPDATE: This trick no longer works because Facebook has changed the structure of photo links!

You've probably seen those "special" Facebook image links that are used to show a picture of your friend to someone else. Such links only lead to the image, not to the owner's profile. But there is a way to find out whose picture it is from that link.

Example:

We have a link like this http://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash4/421311_411689185513622_231039633578579_1806854_1394675137_n.jpg

We don't know whose picture it is because when we go to the link we only see the picture, not the profile.

So what to do?

If we pay attention, the link consists of several groups of numbers separated by an underscore (_). If we count the groups, we will see that there are five.

Now, we count the third group on the left. In this case, it's the number 231039633578579

Further. Copy this link into your browser's address bar http://www.facebook.com/profile.php?id= and add the number we extracted at the end.

In our case, the whole link would look like this: http://www.facebook.com/profile.php?id=231039633578579

And that's the link to the image owner's profile. If you clicked on this link, you saw that it is the page of this blog.

The same principle is with profiles.

Enjoy.