O'Reilly

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

O'Reilly Velocity Conference
Save 20% with discount code AFF20

Recent Features

  • Animated 3D Flipping Menu with CSS

    CSS animations aren't just for basic fades or sliding elements anymore -- CSS animations are capable of much more.  I've showed you how you can create an exploding logo (applied with JavaScript, but all animation is CSS), an animated Photo Stack, a sweet...

  • Creating Scrolling Parallax Effects with CSS

    Introduction For quite a long time now websites with the so called "parallax" effect have been really popular. In case you have not heard of this effect, it basically includes different layers of images that are moving in different directions or with different speed. This leads to a...

Incredible Demos

  • Elegant Overflow with CSS Ellipsis

    Overflow with text is always a big issue, especially in a programmatic environment. There's always only so much space but variable content to add into that space. I was recently working on a table for displaying user information and noticed that longer strings were...

  • HTML5 Placeholder Styling with CSS

    Last week I showed you how you could style selected text with CSS. I've searched for more interesting CSS style properties and found another: INPUT placeholder styling. Let me show you how to style placeholder text within INPUTelements with some unique CSS code. The CSS Firefox...

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!

Recently on David Walsh Blog

  • Prevent Chrome from Translating a Page

    A while back I shared my favorite Google Chrome extension:  Google Art Project.  I've enjoyed seeing beautiful art when I open a new tab -- it's brought genuine happiness to my day, however small that happiness may be.  About a week ago, however, the art presented had...

  • Create Any Type Of Website With These Multi-Purpose Themes

    We have selected what we believe are the very best multipurpose WordPress themes on the market today. Our list contains a number of best sellers, several newcomers that are proving to be highly popular, and a few themes that are ideal for creating the types of...

  • An Introduction to Static Site Generators

    Static site generators seem to have been becoming more and more popular recently, but they’re not one of those ephemeral novelty things that grow in popularity as quickly as they fall into oblivion shortly after. For over a decade, many different projects — 394 of...

  • Automated Tests for Visual Responsive Layouts

    Today it's all about testing. In 2015, many developers knows about TDD and I personally think that testing is one of the key for quality products. But what about testing in a Front-end environment? How do you guys write your tests for a responsive page or...

  • Getting Dicey With Flexbox

    What if you could build complex CSS layouts in minutes? Flexbox is a new CSS layout spec that makes it easy to construct dynamic layouts. With flexbox, vertical centering, same-height columns, reordering, and direction agnosticism are a piece of cake. There's a popular myth floating around that...