Border vs. Outline in CSS🆚

Introduction

• In CSS, both border and outline are used to draw lines around elements, but they serve different purposes and behave differently. This tutorial will guide you through the differences between border and outline, how to use them, and when to choose one over the other.

What is a Border? 🖼️

• Definition:

• A border in CSS is a line that surrounds the content and padding of an element. It is part of the element's box model and affects the layout.

How Borders Work:

• Borders are applied directly to the edges of an element's box. They are included in the element's dimensions and can be styled with different widths, colors, and styles.

• Syntax:

border: width style color;

• Example:

border: 2px solid black;

• Example in Action:

<style>
  .box {
    width: 200px;
    height: 100px;
    border: 3px dashed blue;
  }
</style>
<div class="box">This box has a border.</div>

What is an Outline?✨

• Definition:

• An outline in CSS is a line drawn around the outside of an element. Unlike borders, outlines do not take up space and do not affect the element's size or position in the layout.

How Outlines Work:

• Outlines are drawn outside the element's border and do not interfere with the box model. They are often used for accessibility purposes, such as highlighting focused elements.

• Syntax:

outline: width style color;

• Example:

outline: 2px solid red;

• Example in Action:

<style>

  .box {
    width: 200px;
    height: 100px;
    outline: 3px dotted green;
  }
</style>
<div class="box">This box has an outline.</div>

Key Differences Between Border and Outline🧐

Placement:

• Border: Sits inside the element's box and is part of the element's dimensions.

• Outline: Sits outside the element's box and does not affect the element's dimensions.

Space Consumption:

• Border: Adds to the size of the element, potentially affecting the layout.

• Outline: Does not add to the size of the element and does not affect the layout.

Customizability:

• Border: Can be styled individually for each side (top, right, bottom, left) using properties like border-top, border-right, etc.

• Outline: Is a single line that cannot be customized for each side individually.

Impact on Layout:  

• Border: Since it is part of the box model, it can shift the position of surrounding elements.

• Outline: Being outside the box model, it does not shift the position of surrounding elements.