Example

by cvalleskey

HTML

<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Web/CSS/fit-content -->

<div id="container">
  <div class="large">Item as wide as the content.</div>
  <div>
    Item with more text in it. Because the contents of it are
    wider than the maximum width, it is clamped at 300 pixels.
  </div>
  <div>Flexible item</div>
</div>

CSS

#container {
  display: grid;
  grid-template-columns: fit-content(24ch) fit-content(300px) 1fr;
  grid-gap: 5px;
  box-sizing: border-box;
  height: 200px;
  width: 100%;
  background-color: #8cffa0;
  padding: 10px;
}

#container > div {
  background-color: #8ca0ff;
  padding: 5px;
}

.large {
  font-size: 2em;
}