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prefers-reduced-motion and browser defaults

All the omens were there: a comet in the sky; birds fell silent; dogs howled; unquiet spirits walked the forests and the dark, empty places. Yes, it was a meeting request from Marketing to discuss a new product page with animations that are triggered on scroll.

Much as a priest grasps his crucifix when facing a vampire, I immediately reached for Intersection Observer to avoid the browser grinding to a halt when watching to see if something is scrolled into view. And, like an exoricst sprinkling holy water on a demon, I also cleansed the code with a prefers-reduced-motion media query.

prefers-reduced-motion looks at the user’s operating system settings to see if they wish to suppress animations (for performance reasons, or because animations make them nauseousperhaps because they have a vestibular disorder). A responsible developer will check to see if the user has indicated that they prefer reduced motion and use or avoid animations accordingly.

Content images can be made to switch between animated or static using the <picture> element (so brilliantly brought to you by a team of gorgeous hunks). Bradbury Frosticle gives this example:

  <source srcset="no-motion.jpg" media="(prefers-reduced-motion: reduce)">
  <img srcset="animated.gif alt="brick wall"/>

Now, obviously you are a responsible developer. You use alt text (and don’t call it “alt tags”). But unfortunately, not everyone is like you. There are also 639 squillion websites out there that were made before prefers-reduced-motion was a thing, and only 3 of them are actively maintained.

It seems to me that browsers could do more to protect their users. Browsers are, after all, user agents that protect the visitor from pop-ups, malicious sites, autoplaying videos and other denizens of the underworld. They should also protect users against nausea and migraines, regardless of whether the developer thought to (or had the tools available to).

So, I propose that browsers should never respect scroll-behavior: smooth; if a user prefers reduced motion, regardless of whether a developer has set the media query.

Animated GIFs (and their animated counterparts in more modern image formats) are somewhat more complex. Since 2018, the Chromium-based Vivaldi browser has allowed users to deactivate animated GIFs right from the Status Bar, but this isn’t useful in all circumstances.

My initial thought was that the browser should only show the first five seconds because WCAG Success Criterion 2.2.2 says

For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than five seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it

But this wouldn’t allow a user to choose to see more than 5 seconds. The essential aspect of this success criterion is, I think, control. Melanie Richards, who does accessibility on Microsoft Edge browser, noted

IE had a neat keyboard shortcut that would pause any GIFs on command. I’d be curious to get your take on the relative usefulness of a browser setting such as you described, and/or a more contextual command.

I’m doubtful about discoverability of keyboard commands, but Travis Leithead (also Microsoft) suggested

We can use ML + your mic (with permission of course) to detect your frustration at forever looping Gifs and stop just the right one in real time. Or maybe just a play/pause control would help… +1 customer request!

And yes, a play/pause mechanism gives maximum control to the user. This would also solve the problem of looping GIFs in marketing emails, which are commonly displayed in browsers. There is an added complexity of what to do if the animated image is a link, but I’m not paid a massive salary to make web browsers, so I leave that to mightier brains than I possess.

In the meantime, until all browser vendors do my bidding (it only took 5 years for the <picture> element), please consider adding this to your CSS (by Thomas Steiner)

@media (prefers-reduced-motion: reduce) {
  *, ::before, ::after {
    animation-delay: -1ms !important;
    animation-duration: 1ms !important;
    animation-iteration-count: 1 !important;
    background-attachment: initial !important;
    scroll-behavior: auto !important;
    transition-duration: 0s !important;
    transition-delay: 0s !important;

I am not an MBA, but it seems to me that making your users puke isn’t the best beginning to a successful business relationship.

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One Response to “ prefers-reduced-motion and browser defaults ”

Comment by James C

Agreed re: discoverability of keyboard commands. Although what if the first time a GIF is detected it pops up a little dialog saying “hey you can disable these by [insert instructions]”?

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