Floats

Originally for floating images inside blocks of text, the float property became one of the most commonly used tools for creating multiple column layouts on webpages. With the advent of flexbox and grid it's now returned to its original purpose, as this article explains.

Prerequisites: HTML basics (study Introduction to HTML), and an idea of How CSS works (study Introduction to CSS.)
Objective: To learn how to create floated features on webpages and to use the clear property as well as other methods for clearing floats.

The background of floats

The float property was introduced to allow web developers to implement layouts involving an image floating inside a column of text, with the text wrapping around the left or right of it. The kind of thing you might get in a newspaper layout.

But web developers quickly realized that you can float anything, not just images, so the use of float broadened, for example, to fun layout effects such as drop-caps.

Floats have commonly been used to create entire website layouts featuring multiple columns of information floated so they sit alongside one another (the default behavior would be for the columns to sit below one another in the same order as they appear in the source). There are newer, better layout techniques available. Using floats in this way should be regarded as a legacy technique.

In this article we'll just concentrate on the proper uses of floats.

A float example

Let's explore the use of floats. We'll start with an example involving floating a block of text around an element. You can follow along by creating a new index.html file on your computer, filling it with an HTML template, and inserting the below code into it at the appropriate places. At the bottom of the section, you can see a live example of what the final code should look like.

First, we'll start off with some HTML. Add the following to your HTML body, removing anything that was inside there before:

html
<h1>Float example</h1>

<div class="box">Float</div>

<p>
  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla luctus aliquam
  dolor, eu lacinia lorem placerat vulputate. Duis felis orci, pulvinar id metus
  ut, rutrum luctus orci. Cras porttitor imperdiet nunc, at ultricies tellus
  laoreet sit amet.
</p>

<p>
  Sed auctor cursus massa at porta. Integer ligula ipsum, tristique sit amet
  orci vel, viverra egestas ligula. Curabitur vehicula tellus neque, ac ornare
  ex malesuada et. In vitae convallis lacus. Aliquam erat volutpat. Suspendisse
  ac imperdiet turpis. Aenean finibus sollicitudin eros pharetra congue. Duis
  ornare egestas augue ut luctus. Proin blandit quam nec lacus varius commodo et
  a urna. Ut id ornare felis, eget fermentum sapien.
</p>

<p>
  Nam vulputate diam nec tempor bibendum. Donec luctus augue eget malesuada
  ultrices. Phasellus turpis est, posuere sit amet dapibus ut, facilisis sed
  est. Nam id risus quis ante semper consectetur eget aliquam lorem. Vivamus
  tristique elit dolor, sed pretium metus suscipit vel. Mauris ultricies lectus
  sed lobortis finibus. Vivamus eu urna eget velit cursus viverra quis
  vestibulum sem. Aliquam tincidunt eget purus in interdum. Cum sociis natoque
  penatibus et magnis dis parturient montes, nascetur ridiculus mus.
</p>

Now apply the following CSS to your HTML (using a <style> element or a <link> to a separate .css file — your choice):

css
body {
  width: 90%;
  max-width: 900px;
  margin: 0 auto;
  font:
    0.9em/1.2 Arial,
    Helvetica,
    sans-serif;
}

.box {
  width: 150px;
  height: 100px;
  border-radius: 5px;
  background-color: rgb(207 232 220);
  padding: 1em;
}

If you save and refresh, you'll see something much like what you'd expect: the box is sitting above the text, in normal flow.

Floating the box

To float the box, add the float and margin-right properties to the .box rule:

css
.box {
  float: left;
  margin-right: 15px;
  width: 150px;
  height: 100px;
  border-radius: 5px;
  background-color: rgb(207 232 220);
  padding: 1em;
}

Now if you save and refresh you'll see something like the following:

Let's think about how the float works. The element with the float set on it (the <div> element in this case) is taken out of the normal layout flow of the document and stuck to the left-hand side of its parent container (<body>, in this case). Any content that would come below the floated element in the normal layout flow will now wrap around it instead, filling up the space to the right-hand side of it as far up as the top of the floated element. There, it will stop.

Floating the content to the right has exactly the same effect, but in reverse: the floated element will stick to the right, and the content will wrap around it to the left. Try changing the float value to right and replace margin-right with margin-left in the last ruleset to see what the result is.

Visualizing the float

While we can add a margin to the float to push the text away, we can't add a margin to the text to move it away from the float. This is because a floated element is taken out of normal flow and the boxes of the following items actually run behind the float. You can see this by making some changes to your example.

Add a class of special to the first paragraph of text, the one immediately following the floated box, then in your CSS add the following rules. These will give our following paragraph a background color.

css
.special {
  background-color: rgb(148 255 172);
  padding: 10px;
  color: purple;
}

To make the effect easier to see, change the margin-right on your float to margin so you get space all around the float. You'll be able to see the background on the paragraph running right underneath the floated box, as in the example below.

The line boxes of our following element have been shortened so the text runs around the float, but due to the float being removed from normal flow the box around the paragraph still remains full width.

Clearing floats

We've seen that a float is removed from normal flow and that other elements will display beside it. If we want to stop the following element from moving up, we need to clear it; this is achieved with the clear property.

In your HTML from the previous example, add a class of cleared to the second paragraph below the floated item. Then add the following to your CSS:

css
.cleared {
  clear: left;
}

You should see that the second paragraph now clears the floated element and no longer comes up alongside it. The clear property accepts the following values:

  • left: Clear items floated to the left.
  • right: Clear items floated to the right.
  • both: Clear any floated items, left or right.

Clearing boxes wrapped around a float

You now know how to clear something following a floated element, but let's see what happens if you have a tall float and a short paragraph, with a box wrapped around both elements.

The problem

Change your document so that the first paragraph and the floated box are jointly wrapped with a <div>, which has a class of wrapper.

html
<div class="wrapper">
  <div class="box">Float1</div>

  <p>
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla luctus
    aliquam dolor, eu lacinia lorem placerat vulputate. Duis felis orci,
    pulvinar id metus ut, rutrum luctus orci. Cras porttitor imperdiet nunc, at
    ultricies tellus laoreet sit amet.
  </p>
</div>

In your CSS, add the following rule for the .wrapper class and then reload the page:

css
.wrapper {
  background-color: rgb(148 255 172);
  padding: 10px;
  color: purple;
}

In addition, remove the original .cleared class:

css
.cleared {
  clear: left;
}

You'll see that, just like in the example where we put a background color on the paragraph, the background color runs behind the float.

Once again, this is because the float has been taken out of normal flow. You might expect that by wrapping the floated box and the text of first paragraph that wraps around the float together, the subsequent content will be cleared of the box. But this is not the case, as shown above. To deal with this, the standard method is to create a block formatting context (BFC) using the display property.

display: flow-root

To solve this problem is to use the value flow-root of the display property. This exists only to create a BFC without using hacks — there will be no unintended consequences when you use it.

css
.wrapper {
  background-color: rgb(148 255 172);
  padding: 10px;
  color: purple;
  display: flow-root;
}

Test your skills!

You've reached the end of this article, but can you remember the most important information? You can find some further tests to verify that you've retained this information before you move on — see Test your skills: Floats.

Summary

You now know all there is to know about floats in modern web development. See the article on legacy layout methods for information on how they used to be used, which may be useful if you find yourself working on older projects.