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Joseph Taiwo
Joseph Taiwo

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Getting to know CSS specificity

Have you ever wondered what happens when you apply multiple styles to a single element using different CSS selectors? The browser can't use all the different styles at once, therefore it needs a method to select which style will be applied.

Introduction

In this article, we will discuss Specificity, which is the method that the browser uses to determine which styles will be applied in a situation where there are many styles.

Knowledge of specificity is crucial to developers, as it allows them to know which styles the browser will use in a case where there are multiple styles.

All selectors have a specificity value, and when multiple selectors are used in selecting the same element, the browser chooses the selector with the highest specificity.

Specificity

As the name implies, specificity is a measure of the range of possible values for a condition, this means a specific value is one that is direct and is easier to be understood.

All CSS selectors can be grouped into 4 degrees of specificity:

  • Inline styles (1000)
  • IDs (100)
  • Classes, Attributes, and Pseudo-classes (10)
  • Elements and Pseudo-elements (1)

PS: if you don't know any of the above selectors you could check out my series on CSS selectors.

The arrangement above is known as the specificity hierarchy it is a representation of the specificity of different selectors in descending order.

The values in brackets are known as the specificity hierarchy score of the selector, they are used to calculate the specificity of combined selectors.

Calculating Specificity

When calculating specificity each selector is assigned it's corresponding value in the specificity hierarchy.

Let us take an h1 element with an id of "firstHeader" and a class of "header"

<h1 id="firstHeader" class="header">Tough times never last</h1>
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then apply the following styles to it

h1{
    background-color: green;
}

.header{
    background-color: blue;
}

#firstHeader{
    background-color: red;
}
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Can you guess what color the header is going to be?

Hint: Which selector has the highest value in the specificity hierarchy?

If you guessed red, then you are correct. This is because the red background color was applied with an ID #firstHeader selector, which has a higher specificity value than the class .header and element selectors.

In cases where you have combined selectors, you will need to calculate the combined specificity of the various selectors present.

Combined selectors are selectors that are made by combining 2 or more selectors, they are formed with Combinator selectors

For this case let us consider the second <p> tag in the HTML code below

<div>
    <p class="paragraph" id="firstParagraph">Don't mind me</p>
    <p class="paragraph" id="secondParagraph">Take note of my class and Id</p>
</div>
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Let us use the following combined selectors

div p.paragraph{
    background-color: blue;
    color: white;
}

#secondParagraph{
    background-color: red;
    border: 2px solid black;
}
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The first selector div p.paragraph + p can be broken down and represented as

  • div => Element selector => value = 1
  • p => Element selector => value = 1
  • .paragraph => class selector => value = 10

The specificity of the above selector is the combined specificity of all the selectors present, and in this case, the answer is 12 (1 + 1 + 10).

The second selector #secondParagraph can be broken down as

#secondParagraph => ID selector => value = 100.

Therefore the browser uses the styles in the #secondParagraph selector. Since the specificity value of the #secondParagraph(100) is greater than the specificity value of the div p.paragraph + p (12).

Non-conflicting styles

Specificity is a means of resolving conflicting styles. conflicting styles occur when 2 different selectors try to set a value for a specific property.

Let us take the code we used in the previous section as an example:

div p.paragraph{
    background-color: blue;
    color: white;
}

#secondParagraph{
    background-color: red;
    border: 2px solid black;
}
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Here both selectors assign a value for the background-color property, hence a conflict occurs, and said conflict is resolved by applying the style in the selector with the higher specificity: #secondParagraph.

Since the color property is only present in the first selector, even though it is the selector with a lower specificity since the same style is not present in the selector with a greater specificity, there is no conflict, hence the browser uses the style.

The same goes for the border property in the second selector.

NOTE: When 2 elements have equal specificity the style in the latter is applied

The !important tag

Adding the !important tag to a value automatically makes it the style to be used for that particular property.

For Example:

div p.paragraph{
    background-color: blue !important;
    color: white;
}

#secondParagraph{
    background-color: red;
    border: 2px solid black;
}
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Even though the second selector has a higher specificity, the presence of the !important tag in the background-color property of the first selector still gets applied.

You could say the value of the !important tag in the specificity hierarchy is 10,000 as it overrides all other selectors irrespective of their specificity value.

Conclusion

Knowing how to calculate specificity is a good skill to have, but you do not need to do this every single time as there are tools out there, like specificity calculators that do this job for you.

A personal favorite of mine is the Selectors explained, by Kitty Giraudel, because it not only shows the specificity value but also converts the selector to simple English.

Now that you know how specificity works you can go out there and be rest assured that your selectors will work properly.

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Thank You for reading ❤️

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