Show File Size Information On Attachment Editing Screen

By default, WordPress 3.5 doesn’t specify the file size on the individual attachment’s editing screen. Today I’m sharing with you a tiny snippet that will add exactly that — so now on you’ll be able to know what’s the size of the file you’re looking at.

Attachment Size Metabox

You should add this snippet to your functionality plugin. But yes, it will also work if you place it in your functions.php file within the active theme.