Before position: sticky, we had to finesse around with scroll listeners and bounding box measurements, ugh. But nowadays position: sticky has gained enough browser support to make it a viable option.

As a refresher, these are all the position values the CSS spec has:

.foo {
  position: static|relative|absolute|fixed|sticky;
}

Position sticky header

Basic layout with a header, content, and a footer at the bottom.

<div class="wrap">
  <header class="sticky-header">Sticky header</header>
  <p>Position sticky demo...</p>
  <footer>Footer</footer>
</div>

And the CSS (mandatory lines highlighted):

.wrap {
  border: 1px solid #aaa;
  height: 400px;
}
 
.sticky-header {
  position: sticky;
  top: 20px;
}

It looks like this (scroll down to see the header sticking to the top):

Position sticky footer

More rarely used approach, but elements can also be stuck to the bottom of the page.

Here’s the HTML, pretty much the same as above:

<div class="wrap">
  <header class="header">Sticky header</header>
  <p class="content">Position sticky demo...</p>
  <footer class="footer">Sticky footer</footer>
</div>

We can set the footer position to sticky and bottom to zero:

.wrap {
  display: flex;
  flex-direction: column;
  height: 400px;
}
 
.content {
  flex: 1;
  margin: 20px;
}
 
.footer {
  bottom: 0;
  position: sticky;
}

And the footer stays glued to the bottom:

Position sticky with tables

Table heads (<th>) can be sticky, too. It works exactly the same:

th {
  background-color: rgba(255, 255, 255, 0.9);
  position: sticky;
  top: 0;
}

Position sticky compatibility table:

It’s important to set the background color to the sticky element, or it looks ugly when content scrolls from under it.

A few scenarios where sticky footer doesn’t work

Extra wrapper

Adding an extra wrapping components breaks it, because the stickiness relies on the height of its immediate parent component:

<div class="wrap">
  <!-- This wrapper breaks it -->
  <div>
    <header class="sticky-header">Sticky header</header>
  </div>
  <p>Position sticky demo...</p>
  <footer>Footer</footer>
</div>

Overflow hidden

Setting overflow: hidden to the parent element breaks the sticky.

overflow: hidden is not preventing position: sticky from working. But if you set overflow to hidden on any ancestor of your sticky element, then this ancestor element will be the scrolling container for your sticky element. If you switch the overflow value on your ancestor from hidden to scroll and scroll this ancestor (not the window), then you can see that sticky is still working. — StackOverflow answer.

Conclusions

You could think position sticky as a hybrid of relative and fixed position, at at some point the component’s position changes to fixed, basically the same way we had to do with JavaScript before. Now it’s just built-in.

Sticky has been around for a while now, I found it from a 2015 spec. I remember longingly looking up position sticky from caiuse.com, but it was only supported in Firefox, and maybe Chrome if a flag was set. I guess it just took a while for the browsers to implement it, and now that Edge and Opera are based on Chromium, it’s all of a sudden supported everywhere.