How do I position one image on top of another in HTML?

This is a barebones look at what I've done to float one image over another.

img {
  position: absolute;
  top: 25px;
  left: 25px;
}
.imgA1 {
  z-index: 1;
}
.imgB1 {
  z-index: 3;
}
<img class="imgA1" src="https://via.placeholder.com/200/333333">
<img class="imgB1" src="https://via.placeholder.com/100">

Source


Ok, after some time, here's what I landed on:

.parent {
  position: relative;
  top: 0;
  left: 0;
}
.image1 {
  position: relative;
  top: 0;
  left: 0;
  border: 1px red solid;
}
.image2 {
  position: absolute;
  top: 30px;
  left: 30px;
  border: 1px green solid;
}
<div class="parent">
  <img class="image1" src="https://via.placeholder.com/50" />
  <img class="image2" src="https://via.placeholder.com/100" />
</div>

As the simplest solution. That is:

Create a relative div that is placed in the flow of the page; place the base image first as relative so that the div knows how big it should be; place the overlays as absolutes relative to the upper left of the first image. The trick is to get the relatives and absolutes correct.