Thanks so much for explaining this. I'm trying to retrieve a user's avatar from an external place. However I struggle to find out what the number between the size and the User ID is for, or how I know which one to use. In your first example it's /o/0/512.jpg and in your second one it's /o/196/196224.jpg. Now is there a way to know which number to use there (without being in the XenForo environment)?