background-size
property
Sets the size of background images. cover fills the element; contain fits the entire image.
Syntax
background-size: auto | cover | contain | width height;
Example
css
.cover { background-size: cover; } /* fill, crop */
.contain { background-size: contain; } /* fit, show all */
.exact { background-size: 200px 100px; }
.percent { background-size: 50% auto; }
.hero {
background-image: url('hero.jpg');
background-size: cover;
background-position: center;
}