Our browsers are always evolving and cool new features are added with almost every update. I played around with one of these new features and I love it! I’m talking about the new CSS properties called scroll-timeline and animation-timeline.

MDN explains these properties as:

The scroll-timeline CSS shorthand property is used to define a named scroll progress timeline, which is progressed through by scrolling a scrollable element.
The animation-timeline CSS property specifies the timeline that is used to control the progress of a CSS animation.

In other words, the combination of these two properties makes it possible to control CSS animations with pure CSS and without the need for any JavaScript. This makes a lot of creative ideas possible, without the need for JavaScript.

Think of things like:

Parallax Scrolling Effects
Scroll-based Animations
Sticky Elements with Animated Transitions
Scroll-triggered Video and Media Playback

I’ve been wanting to do something like the second idea for some time already, so during our Google Day (a nice team hackathon) I created a small demo project where an animation is controlled by scrolling. In this article I’ll explain this project in more detail and how it’s done!

Short sidenote : Since this property is fresh off the press, at the time of writing it is not supported by every major browser yet. As always, an up-to-date report can be found at CanIUse. I’ve tried this polyfill for it, but didn’t test it very extensively, so I can’t say too much about it.

Why is this so cool, compared to existing methods?

I can understand you might think something like ‘There are several libraries which do this already, why is this so special’. Of course, there are nice libraries like GSAP, which provide all sorts of controls for animations, but in my opinion, it’s always best to use browser native methods. Besides, all these libraries use JavaScript to achieve this, whereas pure CSS has several advantages, like:

Lesser JavaScript means less Total Blocking Time
CSS is faster to parse and execute
With JavaScript, the layout will be re-rendered, which doesn’t happen with pure CSS

The project: scroll-based animations

So my big idea was to create an animation that can be controlled by scrolling. That is cool and all, but what animation am I going to control and how do I create it? I really like the aesthetics of the Airpod Pro 3 Landing Page, so I rebuilt a part of the animation that is displayed on that page. This is what the result looks like:

You can also check it out yourself on this demo page. Disclaimer: at the moment of writing, this only works on chromium browsers.

How is it done?

The gist of it is actually:

Split a video into separate frames and store them as jpg’s. There are a bunch of tools for this, but I used https://ezgif.com/video-to-jpg.
Create a CSS animation to change the background image of an element to the next frame jpg file at every step
The new and fun part: control that CSS animation with a scroll-timeline.

I’ll explain steps 2 and 3 of this short summary with code examples. Don’t worry, the full repo of this demo is shared at the bottom of the article.

Create the CSS animation**

It might sound like video creation with extra steps (I hope you like this Rick & Morty reference), but to create the CSS animation we will recreate the original video sequence by changing the background-image of an element to the next frame (jpg file) for every step of the animation.

That will look something like:

@keyframes videoAnimation {
  25% {
    background-image: url('frame-1.jpg');
  }
  50% {
    background-image: url('frame-2.jpg');
  }
  75% {
    background-image: url('frame-3.jpg');
  }
  100% {
    background-image: url('frame-4.jpg');
  }
}

A video of 4 frames is very short, even for our Vine generation. The video used in this demo project has 147 frames and writing a new line of CSS for all of these frames doesn’t feel like the most efficient way of working. Luckily, with the power of SCSS, we don’t have to. We create a function that generates this for us, like so (where $frameCount is the amount of frames we have):

@keyframes videoAnimation {
  @for $i from 1 through $frameCount {
    #{math.div($i, $frameCount)*100}% {
      background-image: url('frame-#{$i}.jpg');
    }
  }
}

Control animation with a scroll-timeline

Now that we have the animation, we can start controlling it. We start with this HTML markup:

<div class="container">
  <div class="inner">
    <div class="video"></div>
  </div>
</div>

And the CSS:

.container {
  width: 100vw;
  max-height: 100vh;
  overflow-y: auto;
  scroll-timeline: --videoTimeline y;
}

.inner {
  width: 100%;
  height: 800vh;
}

.video {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-image: url('frame-1.jpg');
  background-size: contain;
  background-repeat: no-repeat;
  background-color: black;
  background-position: center;
  animation-name: videoAnimation;
  animation-duration: 1ms;
  animation-timeline: --videoTimeline;
}

@keyframes videoAnimation {
  25% {
    background-image: url('frame-1.jpg');
  }
  50% {
    background-image: url('frame-2.jpg');
  }
  75% {
    background-image: url('frame-3.jpg');
  }
  100% {
    background-image: url('frame-4.jpg');
  }
}

The magic all happens in the two CSS properties that this whole article is about:

scroll-timeline - with this, we mark the scroll position as a control for other elements
animation-timeline - with this, we tell our CSS that this animation can be controlled by another element’s scroll position, where we refer to the aforementioned scroll-timeline name.

Some other notable points are:

Both.container and .video fill the entire screen
The .container has an overflow-y of auto, to ensure it is scrollable
The height of .inner determines how fast the animation will play when scrolling
The initial background-image of .video is set to the first frame of the video
To keep things CSS, I didn't use the SCSS function for the @keyframes

A possible improvement

A small issue with this approach was that at initial pageload, the images still needed to load when the user scrolled, causing flickering in the video. The solution I implemented probably isn’t the best for production environments. To prevent this from happening, I added a script that preloads all the images. This might need some improvement, but that was not in scope for this demo.

Final Remarks

I really really love this css feature. It performs very well, I dare to say even a lot better than most JavaScript implementations I have seen. I can’t wait for it to be widely supported!

You can find the repo of this demo project here. Feel free to play around, fork, improve and create pr’s! Because ❤️ open source

Because the end result is so nice, thought I'd share it once more here:

Upcoming events

The Test Automation Meetup
PLEASE RSVP SO THAT WE KNOW HOW MUCH FOOD WE WILL NEED Test automation is a cornerstone of effective software development. It's about creating robust, predictable test suites that enhance quality and reliability. By diving into automation, you're architecting systems that ensure consistency and catch issues early. This expertise not only improves the development process but also broadens your skillset, making you a more versatile team member. Whether you're a developer looking to enhance your testing skills or a QA professional aiming to dive deeper into automation, RSVP for an evening of learning, delicious food, and the fusion of coding and quality assurance! 🚀🚀 18:00 – 🚪 Doors open to the public 18:15 – 🍕 Let’s eat 19:00 – 📢 First round of Talks 19:45 – 🍹 Small break 20:00 – 📢 Second round of Talks 20:45 – 🍻 Drinks 21:00 – 🙋‍♀️ See you next time? First Round of Talks: The Power of Cross-browser Component Testing - Clarke Verdel, SR. Front-end Developer at iO How can you use Component Testing to ensure consistency cross-browser? Second Round of Talks: Omg who wrote this **** code!? - Erwin Heitzman, SR. Test Automation Engineer at Rabobank How can tests help you and your team? Beyond the Unit Test - Christian Würthner, SR. Android Developer at iO How can you do advanced automated testing for, for instance, biometrics? RSVP now to secure your spot, and let's explore the fascinating world of test automation together!
December 11 | Coven of Wisdom - Amsterdam
Go to page for The Test Automation Meetup
Coven of Wisdom - Herentals - Winter `24 edition
Worstelen jij en je team met automated testing en performance? Kom naar onze meetup waar ervaren sprekers hun inzichten en ervaringen delen over het bouwen van robuuste en efficiënte applicaties. Schrijf je in voor een avond vol kennis, heerlijk eten en een mix van creativiteit en technologie! 🚀 18:00 – 🚪 Deuren open 18:15 – 🍕 Food & drinks 19:00 – 📢 Talk 1 20:00 – 🍹 Kleine pauze 20:15 – 📢 Talk 2 21:00 – 🙋‍♀️ Drinks 22:00 – 🍻 Tot de volgende keer? Tijdens deze meetup gaan we dieper in op automated testing en performance. Onze sprekers delen heel wat praktische inzichten en ervaringen. Ze vertellen je hoe je effectieve geautomatiseerde tests kunt schrijven en onderhouden, en hoe je de prestaties van je applicatie kunt optimaliseren. Houd onze updates in de gaten voor meer informatie over de sprekers en hun specifieke onderwerpen. Over iO Wij zijn iO: een groeiend team van experts die end-to-end-diensten aanbieden voor communicatie en digitale transformatie. We denken groot en werken lokaal. Aan strategie, creatie, content, marketing en technologie. In nauwe samenwerking met onze klanten om hun merken te versterken, hun digitale systemen te verbeteren en hun toekomstbestendige groei veilig te stellen. We helpen klanten niet alleen hun zakelijke doelen te bereiken. Samen verkennen en benutten we de eindeloze mogelijkheden die markten in constante verandering bieden. De springplank voor die visie is talent. Onze campus is onze broedplaats voor innovatie, die een omgeving creëert die talent de ruimte en stimulans geeft die het nodig heeft om te ontkiemen, te ontwikkelen en te floreren. Want werken aan de infinite opportunities van morgen, dat doen we vandaag.
December 12 | Coven of Wisdom Herentals
Go to page for Coven of Wisdom - Herentals - Winter `24 edition
Mastering Event-Driven Design
PLEASE RSVP SO THAT WE KNOW HOW MUCH FOOD WE WILL NEED Are you and your team struggling with event-driven microservices? Join us for a meetup with Mehmet Akif Tütüncü, a senior software engineer, who has given multiple great talks so far and Allard Buijze founder of CTO and founder of AxonIQ, who built the fundaments of the Axon Framework. RSVP for an evening of learning, delicious food, and the fusion of creativity and tech! 🚀 18:00 – 🚪 Doors open to the public 18:15 – 🍕 Let’s eat 19:00 – 📢 Getting Your Axe On Event Sourcing with Axon Framework 20:00 – 🍹 Small break 20:15 – 📢 Event-Driven Microservices - Beyond the Fairy Tale 21:00 – 🙋‍♀️ drinks 22:00 – 🍻 See you next time? Details: Getting Your Axe On - Event Sourcing with Axon Framework In this presentation, we will explore the basics of event-driven architecture using Axon Framework. We'll start by explaining key concepts such as Event Sourcing and Command Query Responsibility Segregation (CQRS), and how they can improve the scalability and maintainability of modern applications. You will learn what Axon Framework is, how it simplifies implementing these patterns, and see hands-on examples of setting up a project with Axon Framework and Spring Boot. Whether you are new to these concepts or looking to understand them more, this session will provide practical insights and tools to help you build resilient and efficient applications. Event-Driven Microservices - Beyond the Fairy Tale Our applications need to be faster, better, bigger, smarter, and more enjoyable to meet our demanding end-users needs. In recent years, the way we build, run, and operate our software has changed significantly. We use scalable platforms to deploy and manage our applications. Instead of big monolithic deployment applications, we now deploy small, functionally consistent components as microservices. Problem. Solved. Right? Unfortunately, for most of us, microservices, and especially their event-driven variants, do not deliver on the beautiful, fairy-tale-like promises that surround them.In this session, Allard will share a different take on microservices. We will see that not much has changed in how we build software, which is why so many “microservices projects” fail nowadays. What lessons can we learn from concepts like DDD, CQRS, and Event Sourcing to help manage the complexity of our systems? He will also show how message-driven communication allows us to focus on finding the boundaries of functionally cohesive components, which we can evolve into microservices should the need arise.
September 19 | Coven of Wisdom - Utrecht
Go to page for Mastering Event-Driven Design

Controlling your video animations with scroll-timeline and animation-timeline

Why is this so cool, compared to existing methods?

The project: scroll-based animations

How is it done?

Create the CSS animation**

A possible improvement

Final Remarks

Upcoming events

The Test Automation Meetup

Coven of Wisdom - Herentals - Winter `24 edition

Mastering Event-Driven Design

Share

Jobs

Senior Web Developer

.Net Developer

Java Developer

.NET Developer

View all jobs