Finding out if an URL is requested from adress bar or image src?

Question

Bit.ly allows you to view stats for short URLs by attaching a + sign at the end of the URL.

Example: http://bit.ly/1dAtI4q

To look up Stats: http://bit.ly/1dAtI4q+

My question is, if I include this URL in an image src attribute like this:

<img src="http://bit.ly/1dAtI4q"> 

and embed this image on a page and request the page, the stats from bit.ly do not count this request as a click.

They do however count visiting the URL via the browser by pasting the URL in the address bar of the browser.

Question: How do they distinguish between the URL is embedded in an image SRC and someone is visiting the URL?

Answer 1

Bitly can't actually distinguish between when a bitly link is followed to fetch an image src, and when a user really clicks on the link, at least not at the point that it records per-link statistics. Your browser cached the redirect after you first followed the link; that's why the image src didn't record another hit.

Try looking at this page: http://www.ploxiln.net/test.html

and looking up the stats for the image hot-linked through a bitly link: http://bitly.net/GFcvn1+

Now refresh the test page, and refresh the stats. You might need to force a "full" refresh with Ctrl-Shift-R, on the test page.

(Disclaimer - bitly engineer here :)