What is the difference between visibility hidden and display none?

Understanding the differences between `visibility: hidden` and `display: none` is crucial for effective front-end development. Both properties are used to control the visibility of elements in a web page, but they do so in fundamentally different ways. Knowing when to use each can greatly impact the user experience and layout of your application.

Let's delve into the specifics of each property, their effects on layout, accessibility, and performance, along with practical examples and common mistakes developers make.

Definition and Basic Differences

visibility: hidden

The `visibility: hidden` property hides an element from the view but maintains its space in the layout. This means that the element will not be visible to the user, but it will still occupy the same space in the document flow as if it were visible.

display: none

On the other hand, `display: none` removes the element from the document flow entirely. This means that the element will not be rendered on the page, and the space it occupied will be reclaimed by other elements. This can lead to a different layout compared to using `visibility: hidden`.

Practical Examples

To illustrate the differences, consider the following HTML structure:

    
Box 1
    
Box 2
    
Box 3

Now, let's apply both styles to see their effects:

Example 1: visibility: hidden

#box2 {
    visibility: hidden;
}

In this case, "Box 2" will not be visible, but the space it occupies will still be there. The layout will look like this:

• Box 1
• (space for Box 2)
• Box 3

Example 2: display: none

#box2 {
    display: none;
}

Here, "Box 2" is completely removed from the layout. The rendering will appear as follows:

• Box 1
• Box 3

Accessibility Considerations

When considering accessibility, it is important to note how screen readers interpret these styles. Elements with `visibility: hidden` are still part of the accessibility tree, meaning screen readers will still announce them as present but not visible. In contrast, elements with `display: none` are removed from the accessibility tree entirely, making them inaccessible to assistive technologies.

Performance Implications

From a performance standpoint, using `display: none` can be more efficient in terms of rendering, as the browser does not need to allocate space for the element. However, if you frequently toggle visibility for elements, using `visibility: hidden` can be more performant since it avoids the reflow that comes with adding and removing elements from the DOM.

Best Practices

• Use `visibility: hidden` when you want to hide an element but maintain its layout position, such as in dropdown menus or modals where you might want to toggle visibility without affecting surrounding elements.
• Use `display: none` when you want to completely remove an element from the layout, such as in tabbed interfaces where only one tab's content should be visible at a time.
• Be cautious with accessibility; ensure that hidden elements do not confuse users relying on screen readers.
• Consider using CSS classes to manage visibility states effectively, allowing for cleaner and more maintainable code.

Common Mistakes

• Confusing the two properties and using `visibility: hidden` when `display: none` is needed, leading to unexpected layout issues.
• Neglecting accessibility implications, which can result in a poor experience for users relying on assistive technologies.
• Overusing `display: none` for elements that may need to be shown again frequently, which can lead to performance issues due to constant reflows.

In conclusion, understanding the differences between `visibility: hidden` and `display: none` is essential for creating effective and accessible web applications. By applying the right property in the right context, developers can enhance both the user experience and the performance of their applications.