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css - CSS Overflow

A Beginners Guide to Understanding CSS Overflow

Good HTML web design nearly always battles with the idea of content positioning. Part of that thinking involves the way content behaves on the page, or rather within its box per the CSS box model concept. The issue at hand is what to do when your content spills out. This is known as CSS overflow.

In this short guide, you will learn how to use the CSS overflow property in your own design. If you are coming into this completely green, it might be a good idea to read up on the basics with the post CSS Basics for Beginners before diving into the content below.

What is CSS Overflow?

As the name suggests, CSS overflow is when content “overflows” from its intended container. This can cause unexpected issues with your page layout as overflowing content can interfere with the visibility of other elements. You have the option of altering the content and/or the container to mitigate the issue. You can also tap into the CSS toolbox and use the CSS overflow property instead.

Before you see that property in action, it is good to see how a CSS overflow might appear on the screen. In the following image, you can see an HTML render where the text inside a div container simply can’t fit in regards to the applied CSS constraints.

Image showing how CSS overflow can impact other elements.

In the above example, the div has a set width and height. The text that was placed inside the div is so large that it cannot be contained within the div as intended. The extra text you see dropping past the red border is the overflow.

How to Use the CSS Overflow Property?

One important thing to remember about the CSS overflow property is that it is on by default. This is why you could see the text content from the div example above coming through. This means that by not setting the CSS overflow property, it is the same as setting it to the value of “visible” as shown in the example below.

Sample showing the CSS overflow property set to the value of visable.

Setting the CSS Overflow to Hidden

If you wanted to keep the overflow from being displayed on the page, your answer is the “hidden” overflow property value. This tells the browser to ignore the content that flows outside of the specified container.

In the following example, the CSS overflow property is set to hidden. On the HTML page render provided next to this, you can see the extra text is no longer displayed. Instead, it cuts off right at the border. 

Example CSS showing the CSS overflow property set to the value of hidden.

Now, you might ask what to do about that missing content. Now the end-user won’t be able to see the extra text with the overflow set to hidden. Worry not, as there is another CSS property value that can help with this.

Setting the CSS Overflow to Scroll

To provide the extra content back to the end-user, you can use the “scroll” value for overflow. This value will create a scroll bar for the container. Depending on the screen proportions, a vertical and/or horizontal scrollbar will be provided to the container. This provides access to the container content without having it overflow beyond it.

The scrollbars can be seen in the image below where the overflow value of scroll has been applied in the sample CSS.

In this image, the CSS overflow property has been set to scroll which provides a vertical and horizontal scroll bar on the target element.

The CSS Overflow Auto Property

A point of confusion for beginners can come from the scroll and auto overflow property values. Both of these values add scroll bars to the container for content access. The main difference is that the scroll value adds the scrollbar as a constant effect. The “auto” value applies the scrollbar effect automatically when needed.

In the following set of example images, the overflow property value is set to auto. In the first example, the scroll bars are not preset as the height of the div container is enough to fully display the text content. In the second example, the div’s height has been reduced which blocks some of the text content from appearing. The scrollbar effect is automatically applied to the container to allow access to the content. 

The X and Y Overflow Values

The final overflow property values are those of the X and Y-axis. Each respectively deals with the horizontal and vertical aspects of the overflow content.  The “overflow-x” property informs the browser of the left and right positions of the content while the “overflow-y” property instructs on the top and bottom content positions.

In the example shown below, you can see both the overflow-x and overflow-y properties have been set. In the example, the x-axis is set to display scroll bars while the y axis is set to hidden. This would provide a container with just a vertical scroll bar only.

Overflowing with Information

This light tutorial has provided you with a basic understanding of what the CSS Overflow property is and how to use it for your own work. However, that is just the tip of the knowledge base offered at Udacity.

Learning how the CSS box model works is one of the best starting points in CSS. However, other strong items to work with are flexbox, floats, and grids. The articles below can offer great introductory information to help you better understand the options available to you for positioning in CSS.

Remember that each step, success, and even failures help to build your web design muscles. Don’t give up just because you fail or succeed. HTML and CSS allow for a wealth of options to accomplish your goals. Above all, remember to have some fun along the way.

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Even with this bit of CSS knowledge under your belt, there is a vast ocean of abilities waiting for you. Take another step towards building your future. Claim advanced programming skills to tackle your designs. The creativity of programming is allowing people to do even more with their ideas. 

If you want to advance your career, take the first steps by learning to code. Having these skills can help you open doors to those new professional possibilities. Enroll in Udacity’s Intro to Programming Nanodegree today to start the journey.