File with JPG extension acts like a GIF with a cat

Question

I recently came across this image which seems like a normal GIF:

Even imgur stores it as a GIF when I uploaded it here.

But when I saw the link, it was a JPEG image, unlike a GIF than what I had expected!

Here's the link: https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/559307_325955130827518_630404691_n.jpg

Answer 1

This is actually a .gif - look at the headers of the HTTP response.

The MIME type is image/gif

So it doesn't matter what the URL says at the end - it's the MIME type that determines how your browser interprets it.

A lot of sites use this (I guess to throw off harvesters?) imgur.com often reports the wrong extension, for example. Try going to i.imgur.com/yourpic.txt - it should still show up as a proper gif.