Creating a Pure CSS Dropdown Using the :hover Selector

In this tutorial we’re going to be building a basic dropdown button. Here’s a peak at what the final result will look like.

Let’s get started.

Motivations and Introduction

When I first began learning HTML and CSS, creating a dropdown was a magical thing. I didn’t know how to implement one myself, and the random stylesheets I found on the Internet were too long and complicated to understand. It wasn’t until I grasped CSS a bit more that I figured out how to make a dropdown myself. In fact, building a basic dropdown is really easy. Let’s walk through it.

Step 1 — The HTML Components

There are three main components of a basic dropdown: The dropdown menu itself, a button to trigger the dropdown, and a container to wrap it all up. I’ll go over each of these components in detail as we go.

Below is a snippet of HTML showing how all three components fit together:

<!-- dropdown container -->
<div class="dropdown">

    <!-- trigger button -->
    <button>Navigate</button>

    <!-- dropdown menu -->
    <ul class="dropdown-menu">
        <li><a href="#home">Home</a></li>
        <li><a href="#about">About</a></li>
        <li><a href="#contact">Contact</a></li>
    </ul>
</div>

Step 2 — Positioning the Dropdown Menu

The code above showed the HTML we’re going to use for the dropdown. The next step is to position the <ul> so that it sits exactly below the button. We’ll use position: absolute; for this. The Mozilla Docs define absolute positioning as such:

position: absolute
Do not leave space for the element. Instead, position it at a specified position relative to its closest positioned ancestor or to the containing block. Absolutely positioned boxes can have margins, they do not collapse with any other margins.

The CSS snippet below shows us using absolute positioning to set the top of .dropdown-menu to be below the button. Notice .dropdown is given position: relative; so the .dropdown-menu is positioned relative to .dropdown as opposed to the next parent in its family tree (again, check the Mozilla Docs for more details on positioning).

.dropdown {
    position: relative;

    /** Make it fit tightly around it's children */
    display: inline-block;
}

.dropdown .dropdown-menu {
    position: absolute;

    /**
     * Set the top of the dropdown menu to be positioned 100%
     * from the top of the container, and aligned to the left.
     */
    top: 100%;
    left: 0;

    /** Allow no empty space between this and .dropdown */
    margin: 0;
}

And this is what all that looks like in the browser:

CSS Dropdown

Super ugly, but it works. Now that we have our basic layout setup, we can start adding some functional styles.

Step 3 — Showing the Menu on Mouse Hover

In order for our dropdown to be usable, we need to add some styles to show and hide the menu based on user action. To keep things simple, we’re going to make the dropdown appear when the user hovers over the button. The CSS selector :hover (Mozilla Docs) can help us with that.

Note that :hover functionality is not the most mobile friendly since there is no concept of hovering on a touch screen, but for the purpose of keeping this tutorial short, and teaching a bit more about CSS, we’re going to keep it simple and use hover anyway.

/**
 * Apply these styles to .dropdown-menu when user hovers
 * over .dropdown
 */
.dropdown:hover .dropdown-menu {

    /** Show dropdown menu */
    display: block;
}

Let me explain the CSS we added above. The .dropdown:hover selector is triggered when the user’s mouse moves over top of .dropdown. Once this happens, the style display: block; is applied to the last item in the selector .dropdown-menu. So, the parent element is triggering the style and the dropdown menu is what the style is being applied to. Pretty neat huh?

Now that we have the basic functionality in place, let’s make it look good.

Step 4 — More Styles

Although making things pretty isn’t really necessary for this tutorial, it’s always a fun thing to do. Here are a few more styles that make our dropdown a lot more pleasant to use.

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown .dropdown-menu {
    position: absolute;
    top: 100%;
    display: none;
    margin: 0;

    /****************
     ** NEW STYLES **
     ****************/

    list-style: none; /** Remove list bullets */
    width: 100%; /** Set the width to 100% of it's parent */
    padding: 0;
}

.dropdown:hover .dropdown-menu {
    display: block;
}

/** Button Styles **/
.dropdown button {
    background: #FF6223;
    color: #FFFFFF;
    border: none;
    margin: 0;
    padding: 0.4em 0.8em;
    font-size: 1em;
}

/** List Item Styles **/
.dropdown a {
    display: block;
    padding: 0.2em 0.8em;
    text-decoration: none;
    background: #CCCCCC;
    color: #333333;
}

/** List Item Hover Styles **/
.dropdown a:hover {
    background: #BBBBBB;
}

Here is what our changes look like in the browser:

CSS Dropdown

Much better right? A few basic styles go a long way.

Wrap-Up

That’s about it for this tutorial. As mentioned above, this was more of a CSS lesson than anything. I wouldn’t recommend using a hover-triggered dropdown on the web today unless it has a fallback for mobile devices. The next step would be to make it activate on click, instead of hover, which requires some Javascript. If you’d like to see that tutorial just let me know on Twitter or Google Plus.

Thanks for reading and I hope you learned something today!

Update

test6554 on Reddit pointed out that we can also use the Checkbox Hack to make things mobile friendly, which wouldn’t require Javascript at all.

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