Spoiler Prevention with CSS Filters

By  on  
CSS Filter

No one likes a spoiler.  Whether it be an image from an upcoming film or the result of a football match you DVR'd, sometimes you just don't want to know.  As a possible provider of spoiler content, some sites may choose to warn users ahead of time.  Sometimes the article title is prefixed with [SPOILER] text or a something similar.  I've thought of a better way -- use CSS filters to blur spoiler content.

The CSS

CSS filters provide a simple way to blur the spoiler content so that the underlying image or text is not legible:

.spoiler {
	filter: blur(20px);
	transition-property: -webkit-filter;
	transition-duration: .4s;
}
.spoiler:hover, .spoiler:focus {
	filter: blur(0px);
}

You will also note that hovering over the offending content will animate the blur until it's been removed.  Unfortunately CSS filters are only supported in WebKit at the moment, but we can no doubt expect more browser support shortly. Also note the :focus addition -- if you set tabIndex=0 on all .spoiler elements, you can support mobile touch to unblur as well!

This jQuery plugin tipped me off on how to achieve a similar blur within Firefox using SVG:

<img src="ricci.jpg" alt="Christina Ricci" class="spoiler" style="filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'blur\'><feGaussianBlur stdDeviation=\'20\' /></filter></svg>#blur");" />

Not the most beautiful of code but works nonetheless.  Changing the stdDeviation to 0 (via JavaScript) would present the element without blur.

Preventing spoiler content is a very limited case (even more limited in the case the photo is Christina Ricci) but it's good to have a strategy just in case.  I like this strategy because it provides an easy option to the user (hovering) to view the obscured content.

Recent Features

  • By
    Chris Coyier&#8217;s Favorite CodePen Demos II

    Hey everyone! Before we get started, I just want to say it's damn hard to pick this few favorites on CodePen. Not because, as a co-founder of CodePen, I feel like a dad picking which kid he likes best (RUDE). But because there is just so...

  • By
    5 Awesome New Mozilla Technologies You&#8217;ve Never Heard Of

    My trip to Mozilla Summit 2013 was incredible.  I've spent so much time focusing on my project that I had lost sight of all of the great work Mozillians were putting out.  MozSummit provided the perfect reminder of how brilliant my colleagues are and how much...

Incredible Demos

  • By
    CSS Fixed Position Background Image

    Backgrounds have become an integral part of creating a web 2.0-esque website since gradients have become all the rage. If you think gradient backgrounds are too cliche, maybe a fixed position background would work for you? It does provide a neat inherent effect by...

  • By
    Animated AJAX Record Deletion Using Dojo

    I'm a huge fan of WordPress' method of individual article deletion. You click the delete link, the menu item animates red, and the item disappears. Here's how to achieve that functionality with Dojo JavaScript. The PHP - Content & Header The following snippet goes at the...

Discussion

  1. I was actually going to write about this but my only issue is it’s a little buggy in that when you hover over the image initially it the blur radius might change, and then on mouse out the blur will not exceed the limits of the image. It’s a beautiful effect but unfortunately the implementation is not quite there.

  2. Yeah, I like the effect. I did something similar quite a while ago using the text-shadow property to create a “blurry” kind of overlay (http://devseo.co.uk/blog/view/blurry-text-simple-snapshots-with-html-css3) this is a lot more effective, but I don’t like the way it “pops” at the end of the animation before completing the “faded” animation

  3. Very cool but only works in Chrome for me. No dice in Firefox nor IE10.

    Thanks.

    • As the post mentions, this is WebKit-only until Firefox and IE implement CSS filters.

  4. Thanks for the svg filter code. This looks like it could be handy for lots of things. Like Lea Verou’s blurred background behind a semitransparent text–background overlay, over a background image.

  5. The blurr effect is much similar with the “fade effect” like here: http://theweeblytricks.weebly.com/3.html

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!