CSS First Child Selector Not Working? Fix It Here

The issue with your CSS selector .home .red:first-child is that :first-child doesn’t select the first element that has the class “red” - it selects the first child element of the parent if that element also has the class “red”. In your HTML, the first child is <span>blah</span>, which doesn’t have the class “red”, so the selector doesn’t match anything.

To target specifically the first element with class=“red”, you need to use different CSS pseudo-classes that match your intended behavior.

Contents

• Understanding the Problem with :first-child
• Solution 1: Using :first-of-type
• Solution 2: Using CSS4 :nth-child() Syntax
• Solution 3: Using the General Sibling Combinator
• Solution 4: Adding a Class Programmatically
• Comparison of Solutions
• Best Practices and Recommendations

Understanding the Problem with :first-child

The :first-child pseudo-class represents the first element among a group of sibling elements, but it only selects an element IF it is both:

1. The first child of its parent, AND
2. Matches the rest of the selector

In your HTML structure:

<div class="home">
    <span>blah</span>          <!-- This is the first child -->
    <p class="red">first</p>   <!-- This is the first element with class "red" -->
    <p class="red">second</p>
    <p class="red">third</p>
    <p class="red">fourth</p>
</div>

The selector .home .red:first-child fails because the first child <span> doesn’t have the class “red”, so the condition isn’t met.

Key insight: According to the Mozilla Developer Network, “:first-child selects the first element among a group of sibling elements” but only if it matches the selector conditions.

Solution 1: Using :first-of-type

The :first-of-type pseudo-class selects the first element of a specific type within its parent, regardless of whether other elements come before it.

.home .red:first-of-type {
    color: red;
    /* other styles */
}

This works because :first-of-type looks for the first <p> element within .home that also has the class “red”. Since the first <p> element in your structure has the class “red”, this selector will match it.

However, be aware that :first-of-type has limitations - it’s based on element type (tag name), not class. If you had other <p> elements without the “red” class before your first “red” <p>, it wouldn’t work as expected.

Solution 2: Using CSS4 :nth-child() Syntax

CSS Selectors Level 4 introduced support for using selectors inside :nth-child(). This is the most direct way to solve your problem:

.home :nth-child(1 of .red) {
    color: red;
    /* other styles */
}

This syntax means "select the 1st child that matches the selector .red within .home. This is exactly what you’re trying to achieve.

Browser support: This syntax is supported in modern browsers including Chrome 88+, Firefox 75+, Safari 14.1+, and Edge 88+.

For older browsers that don’t support this syntax, you can use a combination approach:

/* For modern browsers */
.home :nth-child(1 of .red) {
    color: red;
}

/* Fallback for older browsers */
.home .red:not(.home .red ~ .red) {
    color: red;
}

Solution 3: Using the General Sibling Combinator

You can use the general sibling combinator (~) to select the first element with a specific class by excluding all subsequent siblings with the same class:

.home .red:not(.home .red ~ .red) {
    color: red;
    /* other styles */
}

This works because:

• .home .red selects all elements with class “red” inside “.home”
• .home .red ~ .red selects all elements with class “red” that come after the first one
• :not() excludes those subsequent elements
• The result is only the first element with class “red”

While this works, it can be less performant than other methods and may be harder to read and maintain.

Solution 4: Adding a Class Programmatically

Sometimes the simplest solution is to add a specific class to the first element programmatically, either through JavaScript or by modifying your HTML:

HTML modification:

<div class="home">
    <span>blah</span>
    <p class="red first-red">first</p>
    <p class="red">second</p>
    <p class="red">third</p>
    <p class="red">fourth</p>
</div>

CSS:

.home .first-red {
    color: red;
    /* other styles */
}

JavaScript approach (if you can’t modify HTML):

// This would run when the page loads
document.addEventListener('DOMContentLoaded', function() {
    const firstRed = document.querySelector('.home .red');
    if (firstRed) {
        firstRed.classList.add('first-red');
    }
});

This approach gives you the most control and performance, but requires additional code.

Comparison of Solutions

Best Practices and Recommendations

1. For modern projects: Use :nth-child(1 of .red) as it’s the most semantic and readable solution.

2. For maximum browser compatibility: Add a class programmatically to the first element with JavaScript.

3. For simple cases: Use :first-of-type if you’re only dealing with element types and don’t need class-specific selection.

4. Avoid: The general sibling combinator approach (~) due to performance issues and poor readability.

5. Consider accessibility: When styling the first element differently, ensure you’re not breaking the visual flow or causing accessibility issues.

6. Test thoroughly: Different solutions may work better in different contexts, so test your chosen approach with your specific HTML structure.

The key takeaway is understanding that :first-child doesn’t work the way many developers intuitively expect - it doesn’t select the first element that matches your selector conditions, but rather selects the first child element IF it happens to match your selector conditions.

Sources

1. MDN Web Docs - :first-child pseudo-class
2. MDN Web Docs - :first-of-type pseudo-class
3. Stack Overflow - CSS selector for first element with class
4. BrowserStack Guide - CSS First Item Selector
5. CSS-Tricks - :first-of-type
6. Weekend Projects - CSS :first-child not working correctly

Conclusion

The .home .red:first-child selector fails because :first-child only matches elements that are both the first child of their parent AND match the rest of the selector. In your case, the first child is a <span> without the “red” class.

To target specifically the first element with class=“red”, you have several effective options:

• Use :nth-child(1 of .red) for the most direct and readable solution
• Add a class programmatically for maximum control and compatibility
• Use :first-of-type if you’re working with element types rather than classes
• Avoid complex selector combinations that hurt performance

Understanding how CSS pseudo-classes work - specifically that they evaluate the element against the selector conditions rather than filtering elements and then applying pseudo-classes - is crucial for writing effective CSS selectors.