Animations should be an enhancement, not critical to a user's understanding

prefers-reduced-motion: Taking a no-motion-first approach to animations

I recognise that my pre code needs a lot of work, so the code samples are difficult to read and ugly right now. I plan to update that code. Apologies in the meantime; hopefully the message is still understandable!

Animations help to breathe life into interactive experiences. Animations, especially when overused and abused, can make people very ill. Through this article, I hope to provide you an approach and guidance to discussing how you/your company use animation thoughtfully and responsibly.

Animations can make people sick πŸ“Œ

I experience benign paroxysmal positional vertigo (BPPV), which is a fancy way of saying, the room can start spinning if I turn my head the wrong way. Another side effect is if a website scrolljacks or has too much animation, I can become dizzy and have to lay down often for the rest of the day. BPPV is one of many vestibular disorders that impact millions of people.

As you can imagine, this can be a problem when you're a frontend engineer and are animating lots of things.

User settings rule all πŸ“Œ

A core accessibility approach of mine is to let the user determine what's best for them and to enable as many user settings as I can. Most operating systems allow us to reduce the motion and have for a very long time.

Mac OS Accessibility Settings with Reduce motion set

The setting has been exposed now to most modern browsers using a media feature called prefers-reduced-motion. prefers-reduced-motion media query acts as any other media query with two possible options:

  1. no-preference (the default): the user has not indicated to "Reduce motion" in their OS and will be served all animations and animations designated explicitly as prefers-reduced-motion: no-preference. [I want to make a critical note here that this is operating on a no-consent model. Ew. The user hasn't necessarily opted into animations. They just haven't checked "Reduce motion." That could be because they like and can tolerate animations, or, it's equally possible the user doesn't know about this setting. So, I want us to make sure we're not assuming that these users necessarily want animations.]
  2. reduce: the user has "Reduce motion" checked in their operating system's Accessibility settings and will be served whatever is in the media query for prefers-reduced-motion: reduce.

What this means is that if we can use prefers-reduced-motion to customise our animations based on user settings.

We will have two parts to our code:

  1. animation, and
  2. prefers-reduced-motion media query.

In CSS, it could look something like this:

/*
Part 1: Animation
Here is where we would put our full animation.
*/


.wordArtRotation {
animation: rotation 2s infinite linear;
}

/*
Part 2: Media query
Here is where we would put our partial or no animation.
*/

@media (prefers-reduced-motion: reduce) {
.wordArtRotation {
animation: none;
}
}

Start with No Motion πŸ“Œ

When I collaborate with a designer/animator on an animation, I first ask, "Is this animation critical to understanding the content?"

When the answer is "No" πŸ“Œ

More often than not, the answer is "no." (It might take some finessing of the conversation, so remember to emphasise that being critical isn't the same thing as being important or nice or aesthetic.) When conceived well, animations should be an enhancement to an explanation.

If the animation isn't critical, then my default code is to include animation: none for all of my animations. In CSS, it could look something like this:

@media (prefers-reduced-motion: reduce) {
.wordArtRotation,
.rainbowWave,
.textFadeIn
{
animation: none;
}
}

Another way it could look is to reverse our thought process. Instead of defaulting to adding animations universally, we can instead only add them for people who have designated no-preference.

The code could look something like this:

/*
Part 1: Animation
Here is where we would put our full animation.
*/


.wordArtRotation {
animation: none;
}

/*
Part 2: Media query
Here is where we would put our partial or no animation.
*/

@media (prefers-reduced-motion: no-preference) {
.wordArtRotation {
animation: rotation 2s infinite linear;
}
}

The difference between the first code block and the second one comes down to browser support. The support for prefers-reduced-motion is fairly strong, but still has some gaps (see Can I Use: Prefers reduced motion). Defaulting to this latter approach will mean that all users will default to no animation, including users whose browsers won't recognise the media query.

The difference is not just in code, but in mindset shift. I won't tell you which one is right for you/your org, but I think this type of differentiation is important for your design system, for example. I find that sharing the technical approach with the designer gets them thinking about how they intend for their animations to exist in different environments (and getting them to cater their animations to user preferences).

To turn these individual conversations into a systemic one, you could include animation principles with guidance around how your design system would like animations to be not only coded, but conceived. Providing this context in your documentation will help to guide better animator/designer-developer collaboration.

Framer Motion sets a good tone for accessibilty in documentation with their Guide to Accessibility.

Animation-specific stylesheet πŸ“Œ

Since we've all agreed that our animations aren't critical to perceiving our page (winky face), we can take that one step further and only serve our users CSS if they are cool with prefers-reduced-motion: no-preference.

Here's what you might include in your HTML file in the <head> tag:

<link
rel="stylesheet"
href="animations.css"
media="(prefers-reduced-motion: no-preference)"
/>

Code snippet from Web.dev: prefers-reduced-motion

What this requires is we've placed all our animations into one CSS file. If our user has indicated "Reduce motion" (and thus, the media query prefers-reduced-motion: reduce is true), then the user isn't even served our stylesheet at all. Separating our CSS animations into its own stylesheet can be a very daunting task on a large codebase, so this could require some heavy refactoring. But if CSS animations is a large part of your codebase, it might also mean huge performance savings!

I love this option because it is putting accessibility and performance on the same teamβ€”as they should be!

When the answer is "Yes" πŸ“Œ

If the animation is critical to understanding, then I ask what other ways we intend to serve up that information, because without alternates, we're excluding anyone who won't be able to see the animation (whether due to physical disability, data/technical restrictions, situational, etc).

Questions I typically ask in response πŸ“Œ

Sometimes this conversation between the person who conceived the animation and the person implementing it doesn't happen. That is a damn shame, because I find that's where we needlessly animate things that add exactly zero value to the conversation.

I also ranked these questions in level of spiciness for no other reason than my entertainment to cater your communication to the context of your conversation.

  • Why is this animation critical? 🌢
  • What other ways can we serve up the critical animation? (e.g., through written text, through a static diagram, etc) 🌢🌢
  • If the animation can't load for someone or they can't see it, what was your plan? 🌢🌢🌢

Most of the time, I'm negotiating a way to get information to be served in more ways. Changing the answer from "yes, this animation is critical to understanding" to "no, this animation is not critical but an enhancement." Remember, accessibility means giving the users as many, diversified options as possible, not determining which option works best for them.

Beyond CSS animations πŸ“Œ

Auto-playing video πŸ“Œ

Auto-playing anything is cruel to both users who experience vestibular disorders and neurodivergent users for whom autoplay can cause major focus issues.

CSS-tricks covers this well with Reduced motion picture technique: take two.

JavaScript animations πŸ“Œ

Now while I am very pro-CSS animations (and think they can handle most standard animations), I recognise that CSS can't handle all types of animations, for example, react-spring animations. I'm not yet an expert in these areas. Instead of taking weeks to learn this all to regurgigate it back to you right now, I wanted to share some existing articles that already do a great job of distilling down this information.

Vanilla JS: window.matchMedia demo from web.dev

React: useReduceMotion Hook by infiniteluke

Further Reading πŸ“Œ

Commentary on prefers-reduced-motion with authors covered that I did not. (Note there will be some introductory overlap)

A List Apart: Accessibility for vestibular disorders
Provides guidance to designing for vestibular disorders with tactical tips

A11y with Lindsey: Reducing motion to improve accessibility
Code snippets with brief rundown on adding a toggle to your page and using localStorage to preserve user setting

Josh Comeau: Accessible Animations in React
React Code snippets

Questions and Corrections πŸ“Œ

For questions, please reach out on Twitter! I can't promise to answer all your questions, but I'll try my best!

For corrections (typos, factual inaccuracies), please file a GitHub issue.

Use the prefers-reduced-motion media query to help guide your animation principles

Thu Mar 18 2021 12:56:13 GMT+0000 (Coordinated Universal Time)

tutorials animation accessibility