What Does !Important Mean in Css

What does !important mean in CSS?

It means, essentially, what it says; that 'this is important, ignore subsequent rules, and any usual specificity issues, apply this rule!'

In normal use a rule defined in an external stylesheet is overruled by a style defined in the head of the document, which, in turn, is overruled by an in-line style within the element itself (assuming equal specificity of the selectors). Defining a rule with the !important 'attribute' (?) discards the normal concerns as regards the 'later' rule overriding the 'earlier' ones.

Also, ordinarily, a more specific rule will override a less-specific rule. So:

a {
    /* css */
}

Is normally overruled by:

body div #elementID ul li a {
    /* css */
}

As the latter selector is more specific (and it doesn't, normally, matter where the more-specific selector is found (in the head or the external stylesheet) it will still override the less-specific selector (in-line style attributes will always override the 'more-', or the 'less-', specific selector as it's always more specific.

If, however, you add !important to the less-specific selector's CSS declaration, it will have priority.

Using !important has its purposes (though I struggle to think of them), but it's much like using a nuclear explosion to stop the foxes killing your chickens; yes, the foxes will be killed, but so will the chickens. And the neighbourhood.

It also makes debugging your CSS a nightmare (from personal, empirical, experience).

When to use the !important property in CSS

This is the real life scenario

Imagine this scenario

1. You have a global CSS file that sets visual aspects of your site globally.
2. You (or others) use inline styles on elements themselves which is usually very bad practice.

In this case you could set certain styles in your global CSS file as important, thus overriding inline styles set directly on elements.

Actual real world example?

This kind of scenario usually happens when you don't have total control over your HTML. Think of solutions in SharePoint for instance. You'd like your part to be globally defined (styled), but some inline styles you can't control are present. !important makes such situations easier to deal with.

Other real life scenarios would also include some badly written jQuery plugins that also use inline styles...

I suppose you got the idea by now and can come up with some others as well.

When do you decide to use !important?

I suggest you don't use !important unless you can't do it any other way. Whenever it's possible to avoid it, avoid it. Using lots of !important styles will make maintenance a bit harder, because you break the natural cascading in your stylesheets.

What are the implications of using !important in CSS?

Yes, I'd say your example of using !important is bad practice, and it's very likely it would cause undesired effects further down the line. That doesn't mean it's never okay to use though.

What's wrong with !important:

Specificity is one of the main forces at work when the browser decides how CSS affects the page. The more specific a selector is, the more importance is added to it. This usually coincides with how often the selected element occurs. For example:

button { 
    color: black; 
}
button.highlight { 
    color: blue; 
    font-size: 1.5em;
}
button#buyNow { 
    color: green; 
    font-size: 2em;
}

On this page, all buttons are black. Except the buttons with the class "highlight", which are blue. Except that one unique button with the ID "buyNow", which is green. The importance of the entire rule (both the color and font-size in this case) is managed by the specificity of the selector.

!important, however, is added at a property level, not a selector level. If, for instance, we used this rule:

button.highlight {
    color: blue !important;
    font-size: 1.5em;
}

then the color property would have a higher importance than the font-size. In fact, the color is more important than the color in the button#buyNow selector, as opposed to the font-size (which is still governed by the regular ID vs class specificity).

An element <button class="highlight" id="buyNow"> would have a font-size of 2em, but a color blue.

This means two things:

1. The selector does not accurately convey the importance of all the rules inside it
2. The only way to override the color blue is to use another !important declaration, for example in the button#buyNow selector.

This not only makes your stylesheets a lot harder to maintain and debug, it starts a snowball effect. One !important leads to another to override it, to yet another to override that, et cetera. It almost never stays with just one. Even though one !important can be a useful short-term solution, it will come back to bite you in the ass in the long run.

When is it okay to use:

• Overriding styles in a user stylesheet.

This is what !important was invented for in the first place: to give the user a means to override website styles. It's used a lot by accessibility tools like screen readers, ad blockers, and more.

• Overriding 3rd party code & inline styles.

Generally I'd say this is a case of code smell, but sometimes you just have no option. As a developer, you should aim to have as much control over your code as possible, but there are cases when your hands are tied and you just have to work with whatever is present. Use !important sparingly.

• Utility classes

Many libraries and frameworks come with utility classes like .hidden, .error, or .clearfix. They serve a single purpose, and often apply very few, but very important, rules. (display: none for a .hidden class, for example). These should override whatever other styles are currently on the element, and definitely warrant an !important if you ask me.

Conclusion

Using the !important declaration is often considered bad practice because it has side effects that mess with one of CSS's core mechanisms: specificity. In many cases, using it could indicate poor CSS architecture.

There are cases in which it's tolerable or even preferred, but make sure you double check that one of those cases actually applies to your situation before using it.

How do you read !important in CSS?

an "!important" declaration (the delimiter token "!" and keyword
"important" follow the declaration) takes precedence over a normal
declaration.

http://www.w3.org/TR/CSS2/cascade.html#important-rules

Basically, where two style rules are the same... it gives the one marked !important greater importance and will apply those styles.

Example

div{
    opacity:0 !important;
}

div.jason{
    opacity:1;
}

The first rule would be applied even though the second rule is more specific (one element + one class as opposed to one element)

Note: IE6 ignores !important when you have two of the same property and one of them is important - it'll always apply the last declaration, whether or not it was marked important. **Added from @BoltClock's comment below.

Warning: !important is a hammer that should only be used when absolutely necessary. Almost always, it is better to use more specific selectors to achieve greater specificity and have your styles applied the way you want. !important can make it very difficult for future developers to find and make changes to your code.

One good use case: !important is great for user-defined styles, where a user wants to manipulate Web site pages in specific way in his browser (say make all the backgrounds black and the text yellow). Without having to worry about specificity, the user can add styles to certain elements (like body) and make the styles render.

More important than !important (a higher level !important)?

No, there is no keyword or other way to make a declaration more important than !important. There is no known activity to change this.

In general, it is possible to override a declaration that has !important by using a rule that also has it and that has higher specificity. However, a declaration in a style attribute has, by definition, higher specificity than any other author declaration. The only way to defeat it is in CSS is to use a user style sheet with !important.

There are non-CSS solutions, but they are rather obvious, such as using JavaScript to simply remove or modify the style attribute.

Is it bad to use !important in a CSS property?

!important is a useful tool, but the drawback is that it's kind of a tool of last resort. So you don't want to over-use it as you'll end up causing headaches down the road for anyone that's maintaining the site.

However, your example is a typical use. What is happening is that the JS is injecting inline style attributes on the fly. As such, that's over-riding the cascade in your CSS. !important allows you to over-ride that.

What does `!important` without a value mean in CSS?

I think you’re missing variables.

Check what the original SASS is. It’s probably something like:

border-width: $border-width !important;

But your value for the $border-width variable is an empty string (if it were completely undefined it wouldn’t compile)

CSS specificity and !important

Styles for a directly targeted element will always take precedence over inherited styles, regardless of the specificity of the inherited rule.

-- Specificity: Directly targeted elements vs. inherited styles

Note: the addition of the new contrived ruleset in Demo:

div.outer.outer.outer>div.inner1>div.inner2.inner2>aside.inner3 {
  color: blue !important
}

It has an incredibly ridiculously unnecessarily huge specificity score of 0,0,7,4 and !important as well. CSS reads from right to left:

1. Find an <aside> tag with the class of .inner3
2. It must have a parent <div> that has the class of .inner2.
3. Also that <div class="inner2">must have a parent <div> with a class of .inner1.
4. And it's imperative that <div class="inner1"> have a parent <div> with the class of .outer.

All of these specific rules of the selector must be met just so a deeply nested <aside> tag gets its style. Any descendant elements of .inner3 will inherit color: blue property and value, but it is easily overridden by the likes of i.inner2 with color:red.

   <div class="inner3">
     <p>This deeply nested text has <i class='inner2'>crazy specificity but this text is red.</i>
       ...
     </p>
   </div>

Note: the new ruleset at the bottom of CSS box:

  div {
    color: black !important
  }

Now this selector is specific to all divs so here is how !important has just been assigned a selector with a far reaching scope. This is probably more like the behavior you were expecting.

BTW, you probably noticed the duplicate classes:

  .outer.outer.outer

That is called selector chaining which will increase a selector's specificity score. See Online Specificity Calculator.

Demo

div.outer.outer.outer>div.inner1>div.inner2.inner2>aside.inner3 {  color: blue !important}
.outer .inner1 {  color: green !important;}
.outer .inner1 .inner2 {  color: red;}
div {  color:black !important;}

<head>  <link href="css/style.css" rel="stylesheet">  <link href="css/style1.css" rel="stylesheet"></head>
<body>  <div class="outer">    <div class="inner1">      This text will be green...      <div class="inner2">        <p>Voluptate labore cupidatat an enim quamquam ut anim malis, varias id sed veniam quibusdam, singulis aliqua ut singulis domesticarum, id aliqua illum o officia, et ab domesticarum, irure e excepteur o eram nam appellat coniunctione do commodo..        </p>
        <aside class='inner3'>          <p>This deeply nested text has <i class='inner1'>crazy specificity</i>, yet it only applies to it and its descendants with no specific <b class='inner2'>`color` property</b>.</p>        </aside>      </div>      ...and this text will be green as well.    </div>  </div>