For fun I decided to look at YouTube's thumbnails to see if I could extract useful information out of them and I've come to an interesting find: YouTube does not use libjpeg to encode the images.

The way I determined this was by using jpegtran -optimize on the image and finding that jpegtran produced a file 4 bytes larger. also, a diff of the bytes shows differences all over the place.

Anyone know of any jpeg encoders besides libjpeg(-turbo)?