The CSS property that allows a user to manually resize an element's dimensions is `resize`.
The property controls whether an element can be resized and which directions are permitted. Common values include `both`, `horizontal`, `vertical`, and `none`. For example, `resize: both` lets a user change an element's width and height with a browser-provided handle.
The property is especially familiar from HTML `<textarea>` elements, which many browsers make resizable by default. Authors can disable that behavior with `resize: none`, or restrict it to one direction. A resizable element generally also needs an `overflow` value other than `visible` or `clip`; this is why examples often pair `resize` with `overflow: auto` or `overflow: scroll`.
A common mix-up is `transform`, which can visually scale an element but does not provide a user-controlled resizing handle or change layout dimensions in the same way. `overflow` manages content that exceeds a box; it is often a supporting requirement, not the property that enables resizing itself.