he resize property—part of the CSS3 UI module—allows you to specify how a textarea is resized. It is now supported by all major browsers except IE and iOS Safari.
Note that, by default, webkit browsers and Firefox 4 allow for textareas to be resized, both vertically and horizontally.
textarea { resize: vertical; }
Possible Values
here is the link these are resize property how is this worked click below codepen.io/RamuStar/pen/BaZzegj