Markus Oberlehner
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Simple Solution to Prevent Body Scrolling on iOS

In my last article about building accessible popup overlays with Vue.js we used a simple technique to prevent scrolling in the background. I think that this little trick for preventing scrolling on the <body> element on all devices, including iOS 12 and below (finally, this was fixed in iOS 13 🎉) is worth taking a closer look.

Usually, we can use overflow: hidden on the <body> element to prevent scrolling. But unfortunately, that does not work on older versions of iOS.

In this article, we check out which possibilities we have to prevent scrolling in all browsers, including mobile devices like iPhones and Android-powered smartphones.

Approaches

The most straightforward way for disabling scrolling on websites is to add overflow: hidden on the <body> tag. Depending on the situation, this might do the job well enough. If you don’t have to support older versions of iOS, you can stop reading here.

// src/utils/scroll-lock.js
const $body = document.querySelector("body");

export default {
  enable() {
    $body.style.overflow = "hidden";
  },
  disable() {
    $body.style.removeProperty("overflow");
  },
};

Another way of how to deal with this problem is to use the body-scroll-lock package. This is definitely the most bulletproof way how you can do this. But it comes with the downside of being a pretty complicated solution, which adds 1.1 kB to your final bundle.

Next, we take a look at a not very elegant but simple solution to this problem.

The simple solution for preventing scrolling on iOS

The final size this solution adds to our bundle is only 253 bytes, so significantly less than the body-scroll-lock package.

// src/utils/scroll-lock.js
const $body = document.querySelector("body");
let scrollPosition = 0;

export default {
  enable() {
    scrollPosition = window.pageYOffset;
    $body.style.overflow = "hidden";
    $body.style.position = "fixed";
    $body.style.top = `-${scrollPosition}px`;
    $body.style.width = "100%";
  },
  disable() {
    $body.style.removeProperty("overflow");
    $body.style.removeProperty("position");
    $body.style.removeProperty("top");
    $body.style.removeProperty("width");
    window.scrollTo(0, scrollPosition);
  },
};

As you can see above, we use position: fixed in combination with storing the scroll position of the user so we can restore the scroll position after the fact.

Caveats

There are certainly some downsides to this approach. If you change the size of the browser window while the scroll lock is active, for example, the scroll position does not get restored correctly.

Another thing we have to consider is that setting CSS styles on the body triggers painting in the browser. I don’t think this is a big deal in most cases. But if you need to lock and unlock scrolling very frequently (every couple seconds), this might hurt the frame rate of your application.

But the most critical caveat you have to keep in mind is that this approach changes certain styles on the <body> element. If you apply custom styles for overflow, position, top, or width, your styles might break when the scroll lock is enabled.

Furthermore, there might be some edge cases I didn’t think of, and the developers of body-scroll-lock have. But until this point, I got along pretty well using this approach on a couple of sites.

Wrapping it up

It’s unfortunate that for a long time, only using overflow: hidden to prevent scrolling did not work on iOS. But with only 18 lines of JavaScript, we can work around the problem.

In the end, you must decide if it is even necessary in your case to support older versions of iOS. Luckily, iOS users usually do update very quickly.

Ressources