Why does bottom:0 not work when using position:sticky?

In this article, we’ll explain why setting bottom:0 doesn’t work when using position:sticky. position:sticky is a CSS positioning property that fixes an element’s position when scrolled to a specific position. bottom:0 sets an element’s distance from the bottom of its container. However, in some cases, applying bottom:0 to position:sticky elements doesn’t work. We’ll delve deeper into this issue and provide examples to explain why.

Read more: CSS Tutorial

What is position:sticky?

First, let’s briefly review how position:sticky works. When we set the position property to sticky on an element, it creates a gap between relative and fixed positioning. The element will be relatively positioned until scrolling reaches the specified position, but once scrolling reaches the specified position, it will become fixed. This allows the element to remain in its fixed position until scrolling reaches another specified position.

Why doesn’t bottom:0 work?

The bottom:0 property of a position:sticky element is commonly used to position an element relative to the bottom of its container. However, when we try to apply bottom:0 to a position:sticky element in certain situations, it doesn’t work. This is because the bottom:0 property of a position:sticky element positions the element relative to its immediate parent container.

By default, a position:sticky element is positioned relative to its containing block and not beyond the boundaries of its immediate parent container. Therefore, if we want the bottom:0 property of a position:sticky element to work, we need to ensure that the height of its immediate parent container is large enough to exceed the distance from the bottom of the position:sticky element.

Here’s an example of why bottom:0 doesn’t work in some cases:

<style> 
.container { 
height: 200px; 
overflow: auto; 
} 

.sticky-element { 
position: sticky; 
bottom: 0; 
background-color: #f0f0f0; 
padding: 10px; 
} 
</style> 

<div class="container"> 
<div> 
<p>Scroll down to see the sticky element at the bottom. </p> 
<!-- Some content --> 
</div> 
<div class="sticky-element"> 
Sticky Element 
</div> 
</div> 

In the example above, we have a container with a height of 200px and a position:sticky element inside it that we want to position at the bottom of the container. However, because the container isn’t tall enough to contain the position:sticky element, setting bottom:0 won’t work. We can fix this by adjusting the height of the container.

.container {
height: 400px;
overflow: auto;
} 

By adjusting the height of the container to 400px, the bottom:0 property of the position:sticky element now correctly sticks to the bottom of the container.

Summary

In this article, we explained why setting bottom:0 doesn’t work when using position:sticky. We learned that the bottom:0 property of a position:sticky element can only be positioned relative to its immediate parent container, and that the height of the container needs to be large enough to contain the position:sticky element. By understanding these reasons, we can correctly use the position:sticky and bottom:0 properties to keep the element fixed to the bottom of the container when scrolling.