Mastering Scrolling Behavior with CSS Scroll Snap Stop

What is scroll snap?

Imagine a webpage with content that can't be fully displayed on a single screen. Scrolling allows you to navigate through this content. Scroll snap is a CSS feature that lets you define how the scrolling behaves when the user stops interacting with the scrollbar.

What does "scroll-snap-stop" do?

This property determines what part of the scrolling content snaps into view when the scrolling stops. It essentially defines where the scrolling animation should end.

Possible values for "scroll-snap-stop"

There are three main options for "scroll-snap-stop":

• never
  Scrolling momentum is never interrupted by snap points. This allows for natural scrolling but might prevent content from aligning perfectly.
• always
  Scrolling always stops at a snap point, regardless of the user's momentum. This can feel more controlled but might restrict free scrolling.
• normal (default)
  This is the most common setting. Scrolling stops at the nearest snap point, which is usually the element's edge.

Why use "scroll-snap-stop"?

This property is useful for creating layouts where you want content to snap to specific positions during scrolling. For instance, you can use it with carousels or image galleries where you want each item to be centered on the screen when scrolling stops.

• Be sure to test your implementation on different devices and browsers as compatibility might vary.
• Using "scroll-snap-stop" can impact user experience. While it creates a cleaner look, it might feel less intuitive if users are accustomed to freely scrolling.

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HTML Structure

<article class="scroller">
  <section><h2>Section One</h2></section>
  <section><h2>Section Two</h2></section>
  <section><h2>Section Three</h2></section>
</article>

This code defines an article element with the class "scroller" which will act as our scrollable container. Inside, we have three sections containing headings.

CSS Styles

.scroller {
  height: 300px; /* Limit the height to create scrolling */
  overflow-y: scroll; /* Enable scrolling on the y-axis */
  scroll-snap-type: y mandatory; /* Enable mandatory snapping on y-axis */
}

.scroller section {
  scroll-snap-align: start; /* Snap to the top of each section */
  /* Add styling for sections like background color, padding, etc. */
}

/* Here's where we play with scroll-snap-stop */
.scroller {
  scroll-snap-stop: always; /* Try changing this value to see the effect */
}

• The sections within the scroller have scroll-snap-align: start applied, making them snap to the top edge when scrolling stops.
• Scroll snapping is enabled with scroll-snap-type: y mandatory which specifies snapping along the vertical axis and makes it mandatory.
• We define styles for the scroller element, setting its height and enabling scrolling.

Now comes the interesting part:

• We set scroll-snap-stop: always on the scroller. This ensures scrolling always stops at a snap point, regardless of momentum.

Testing the Code

• Open the HTML file in a web browser.
• Save the HTML and CSS code in separate files (e.g., index.html and styles.css).

Now, when you scroll through the sections, you'll notice that scrolling stops precisely at the beginning of each section, showcasing the effect of "scroll-snap-stop: always".

• Remove scroll-snap-stop altogether. This will allow for natural scrolling without any interruption at snap points.
• Try changing the value of scroll-snap-stop to "normal" and observe how scrolling behaves. In this case, it will stop at the nearest snap point based on momentum.

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JavaScript for Scrolling

• Use JavaScript libraries like Flickity or iScroll.js to manage scrolling behavior. These libraries offer features like snapping, momentum control, and custom animations. This approach provides more flexibility but requires additional JavaScript code.

Combining scroll-snap-type and scroll-padding

• Utilize scroll-snap-type to define snap points and scroll-padding on the container to create a buffer zone around the content. This prevents accidental overscrolling past the intended snap points. It's a good alternative to "always" in "scroll-snap-stop" as it allows for some momentum-based scrolling while still snapping to specific positions.

Fixed-Height Elements with Overflow

• Set a fixed height for each section or element you want to snap to. Then, use overflow: hidden on those elements to hide any content exceeding the height. This creates a stepping effect where content "jumps" into view as you scroll. This approach is simpler but might not be suitable for elements with dynamic content or varying heights.

Choosing the Right Alternative

The best alternative depends on your project requirements:

• For a straightforward, fixed-position effect, fixed-height elements might suffice.
• For simpler snapping with some momentum control, combining scroll-snap-type and scroll-padding is a good alternative.
• If you need fine-grained control over snapping behavior and animations, JavaScript libraries are a good choice.