Introduction to the CSS outline properties: A Guide to Styling Your Webpage with examples
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CSS Outline is a way to add a visible border around an HTML element, but outside of the element's regular border. It can be used to highlight elements on a webpage, provide visual cues to the user, and improve the accessibility of your website.
Essentially, it is a tool that allows you to add an extra layer of styling to elements on your webpage.
In this post, we'll explore what CSS Outline is, how to use it, its benefits, and common mistakes to avoid.
What is CSS Outline?
An outline is a line that is drawn around elements, OUTSIDE the borders, to make the element “stand out”.
CSS Outline Properties
The CSS Outline property has several sub-properties that you can use to customize the outline's appearance. The most commonly used properties are:
- outline-style: This property defines the style of the outline, such as solid, dotted, or dashed.
- outline-color: This property defines the color of the outline.
- outline-width: This property defines the width of the outline.
- outline-offset: This property defines the distance between the outline and the element's border.
Note: Outline differs from borders! Unlike the border, the outline is drawn outside the element's border, and may overlap other content. Also, the outline is NOT a part of the element's dimensions; the element's total width and height is not affected by the width of the outline.{alertSuccess}
CSS Outline Style
CSS outline-style is a property that allows you to customize the appearance of the outline around an HTML element. There are several values you can use for this property, including:
| dotted | Defines a dotted outline |
| dashed | Defines a dashed outline |
| solid | Defines a solid outline |
| double | Defines a double outline |
| groove | Defines a 3D grooved outline |
| ridge | Defines a 3D ridged outline |
| inset | Defines a 3D inset outline |
| outset | Defines a 3D outset outline |
| none | Defines no outline |
| hidden | Defines a hidden outline |
The following example shows the different outline-style values:
Example
Demonstration of the different outline styles:
p.dotted {outline-style: dotted;}p.dashed {outline-style: dashed;}p.solid {outline-style: solid;}p.double {outline-style: double;}p.groove {outline-style: groove;}p.ridge {outline-style: ridge;}p.inset {outline-style: inset;}p.outset {outline-style: outset;}{codeBox}
Result:
A dotted outline.
A dashed outline.
A solid outline.
A double outline.
A groove outline. The effect depends on the outline-color value.
A ridge outline. The effect depends on the outline-color value.
An inset outline. The effect depends on the outline-color value.
An outset outline. The effect depends on the outline-color value.
CSS Outline Width
The outline-width property determines the width of the outline and can have one of the following values:
- thin (typically 1px)
- medium (typically 3px)
- thick (typically 5px)
- A specific size (in px, pt, cm, em, etc)
The following example shows some outlines with different widths:
A thin outline.
A medium outline.
A thick outline.
A 4px thick outline.
Example
<!DOCTYPE html><html><head><style>p.ex1 {border: 1px solid black;outline-style: solid;outline-color: red;outline-width: thin;}p.ex2 {border: 1px solid black;outline-style: solid;outline-color: red;outline-width: medium;}p.ex3 {border: 1px solid black;outline-style: solid;outline-color: red;outline-width: thick;}p.ex4 {border: 1px solid black;outline-style: solid;outline-color: red;outline-width: 4px;}</style></head><body><h2>The outline-width Property</h2><p class="ex1">A thin outline.</p><p class="ex2">A medium outline.</p><p class="ex3">A thick outline.</p><p class="ex4">A 4px thick outline.</p></body></html>{codeBox}
CSS Outline Color
The outline-color property is used to set the color of the outline.
The color can be set by:
| name | specify a color name, like "red" |
| HEX | specify a hex value, like "#ff0000" |
| RGB | specify a RGB value, like "rgb(255,0,0)" |
| HSL | specify a HSL value, like "hsl(0, 100%, 50%)" |
| invert | performs a color inversion (which ensures that the outline is visible, regardless of color background) |
The following example displays various outlines with different colors. Also, notice that these elements also have a thin black border inside the outline:
A solid red outline.
A dotted blue outline.
An outset grey outline.
Example
<!DOCTYPE html><html><head><style>p.ex1 {border: 2px solid black;outline-style: solid;outline-color: red;}p.ex2 {border: 2px solid black;outline-style: dotted;outline-color: blue;}p.ex3 {border: 2px solid black;outline-style: outset;outline-color: grey;}</style></head><body><h2>The outline-color Property</h2><p>The outline-color property is used to set the color of the outline.</p><p class="ex1">A solid red outline.</p><p class="ex2">A dotted blue outline.</p><p class="ex3">An outset grey outline.</p></body></html>{codeBox}
HEX Values
The outline color can also be specified using a hexadecimal value (HEX):
Example
p.ex1 {outline-style: solid;outline-color: #ff0000; /* red */}{codeBox}
RGB Values
Or by using RGB values:
Example
p.ex1 {outline-style: solid;outline-color: rgb(255, 0, 0); /* red */}{codeBox}
HSL Values
You can also use HSL values:
Example
p.ex1 {outline-style: solid;outline-color: hsl(0, 100%, 50%); /* red */}{codeBox}
CSS Outline - Shorthand property
The outline property is a shorthand property for setting the following individual outline properties:
- outline-width
- outline-style (required)
- outline-color
The outline property is specified as one, two, or three values from the list above.
The order of the values does not matter.
The following example shows some outlines specified with the shorthand outline property:
A dashed outline.
A dotted red outline.
A 5px solid yellow outline.
A thick ridge pink outline.
Example
p.ex1 {outline: dashed;}p.ex2 {outline: dotted red;}p.ex3 {outline: 5px solid yellow;}p.ex4 {outline: thick ridge pink;}{codeBox}
outline-offset - CSS: Cascading Style Sheets
The outline-offset property adds space between an outline and the edge/border of an element. The space between an element and its outline is transparent.
The following example specifies an outline 15px outside the border edge:
This paragraph has an outline 15px outside the border edge.
Example
p {margin: 30px;border: 1px solid black;outline: 1px solid red;outline-offset: 15px;}{codeBox}
The following example shows that the space between an element and its outline is transparent:
This paragraph has an outline of 15px outside the border edge.
Example
p {margin: 30px;background: yellow;border: 1px solid black;outline: 1px solid red;outline-offset: 15px;}{codeBox}
CSS outline properties: best practices
Here are some best practices for using CSS Outline properties:
- Use outlines appropriately: Outlines should be used to highlight interactive elements, such as links, buttons, and form controls. They should not be used for decorative purposes or to add borders around non-interactive elements.
- Customize outlines: Outlines should be customized to fit your website's design and aesthetic. This can be done by adjusting the width, color, and style of the outline.
- Keep outlines visible: Outlines should not be hidden using CSS, as this can create accessibility issues for users who rely on keyboard navigation. Outlines should be visible and used appropriately.
- Test with keyboard navigation: When using outlines to improve accessibility, it's important to test your website with keyboard navigation to ensure that users can easily see and interact with the outlined elements.
- Don't make outlines too thick: Outlines that are too thick can overpower other design elements on your website and make it difficult for users to distinguish between elements. As a general rule, outlines should be no more than 2-3 pixels thick.
By following these best practices, you can effectively use CSS Outline properties to improve the accessibility and user experience of your website.
Remember to use outlines appropriately, customize them to fit your website's design, and test them with keyboard navigation to ensure they are effective for all users.
CSS outline properties: avoid common mistakes
Here are some common mistakes to avoid when using CSS outline properties:
- Hiding outlines: Outlines should not be hidden using CSS, as this can create accessibility issues for users who rely on keyboard navigation. Outlines should be visible and used appropriately.
- Making outlines too thick: Outlines that are too thick can overpower other design elements on your website and make it difficult for users to distinguish between elements. As a general rule, outlines should be no more than 2-3 pixels thick.
- Using outlines for decorative purposes: Outlines should be used to highlight interactive elements, such as links, buttons, and form controls. They should not be used for decorative purposes or to add borders around non-interactive elements.
- Overriding user preferences: Some users may have specific preferences for the appearance of outlines or may have disabled them altogether. It's important to avoid overriding these preferences and ensure that your website is accessible for all users.
- Applying outlines to non-interactive elements: Outlines should only be applied to interactive elements, as applying them to non-interactive elements can be confusing for users and create unnecessary visual clutter.
By avoiding these common mistakes, you can effectively use CSS outline properties to improve the accessibility and user experience of your website. Remember to use outlines appropriately, avoid making them too thick, and ensure that your website is accessible for all users.
Conclusion:
In conclusion, CSS Outline is a powerful tool that can help you improve the accessibility and user experience of your website.
By using CSS Outline, you can add an extra border around HTML elements, outside of their regular borders, and customize the appearance of the outline to fit your website's design.
This can help provide visual cues to users, highlight important elements, and make it easier for users who rely on keyboard navigation to interact with your website.
However, it's important to use CSS Outline sparingly and avoid common mistakes, such as hiding outlines or making them too thick. By following best practices for using CSS Outline, you can create a website that looks great and functions well for all users.
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