<div class='slider'>
<img
      src="https://images.unsplash.com/photo-1525382455947-f319bc05fb35?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=800&q=60"
    />
    <img
      src="https://images.unsplash.com/photo-1504713721722-f73b4ccdfe6a?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=800&q=60"
    />
    <img
      src="https://images.unsplash.com/photo-1532458198880-add09ce3b2f5?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=2250&q=80"
    />
    <img
      src="https://images.unsplash.com/photo-1524767615-3d4139c938a3?ixlib=rb-1.2.1&auto=format&fit=crop&w=2255&q=80"
    />
</div>

.slider {
    display: flex;
    
    width: 100%;
    height: 100vh;
}

.slider img {
  flex: 0 0 100%;
  width: 100%;
  object-fit: cover;
}

// fix para CodePen
body { margin: 0; }