Meta: 1:1

Refers to any image with a 1:1 aspect ratio, which means that the picture is a perfect square (when the width is the same as the height). This tag was invalidated (forum #183129), but no longer aliases to invalid_tag.

Posts with a 1:1 aspect ratio can easily be searched for as ratio:1, although that metatag includes posts that are not exactly 1:1. If any post is even one pixel off by width or height, it's not a perfect square and thus doesn't get this tag.