Bootstrap - Images


Responsive Images

Bootstrap makes it easy to create responsive images that adjust to fit the size of the device or screen they are viewed on. By applying specific classes to your images, you can make sure that they scale properly and maintain their aspect ratio across different devices.

To make an image responsive in Bootstrap, you can add the .img-fluid class to the <img> tag. The .img-fluid class applies max-width: 100%; and height: auto; to the image, allowing it to scale down if necessary while maintaining its aspect ratio. This means that the image will never be wider than its parent container, preventing horizontal scrolling on smaller screens.

.img-fluid Class Example

<img src="image.jpg" class="img-fluid" alt="Responsive Image">

In older versions of Bootstrap (version 3), the .img-responsive class was used instead of .img-fluid. The .img-responsive class has similar functionality, setting max-width: 100%; and height: auto; on the image to make it responsive. However, in Bootstrap 4 and later versions, .img-fluid is the recommended class for responsive images.

By applying the .img-fluid or .img-responsive class to your images, you can create flexible and responsive layouts that adapt to different screen sizes. This is useful when building mobile-friendly websites or web applications, as it helps to optimize the display of images on smaller devices.

Remember to always include meaningful alt text for your images to improve accessibility and provide context for users who may not be able to see the images.

With Bootstrap's responsive image classes, you can easily create images that look great and adapt seamlessly across a wide range of devices and screen resolutions.

Image Shapes

Bootstrap has classes that let you apply different shapes to your images. You can add rounded corners, make circular images, or style images as thumbnails.

Rounded Corners

To add rounded corners to an image, use the .rounded class. This class adds a small border radius to the corners of the image, making it a bit rounded.

Example: Rounded Corners

<img src="image.jpg" class="rounded" alt="Rounded Image">

Bootstrap has more classes like .rounded-top, .rounded-right, .rounded-bottom, and .rounded-left. These classes let you add rounded corners to specific sides of the image.

You can also change the border radius by using the .rounded-* classes, where * can be replaced with a size value such as sm (small), lg (large), or a custom pixel value like 10. For example, .rounded-lg makes the border radius larger than the default .rounded class.

Circle Images

You can make circular images with the .rounded-circle class. By adding this class to an image, it will be styled as a perfect circle, with equal width and height.

Example: Circle Images

<img src="avatar.jpg" class="rounded-circle" alt="Circle Image">

The .rounded-circle class is useful for showing user avatars or profile pictures in a circular format.

Thumbnail Images

Bootstrap lets you style images as thumbnails using the .img-thumbnail class. This class adds a rounded border, padding, and a subtle box shadow to the image, giving it a thumbnail-like look.

Example: Thumbnail Images

<img src="thumbnail.jpg" class="img-thumbnail" alt="Thumbnail Image">

Thumbnail images are often used to show a small preview or a group of images in a grid or gallery layout.

By using these Bootstrap classes, you can quickly apply different shapes to your images, such as rounded corners, circles, and thumbnails. These classes help add visual style to your web pages without needing custom CSS.

Choose the right class based on your design needs and combine them with other Bootstrap classes and custom styles to get the look you want for your images.

Aligning Images

Bootstrap has classes that let you align images to the left, right, or center of a container. You can use floating classes or a combination of margin and display classes to get the image alignment you want.

To align an image to the left or right of its container, you can use the .float-left or .float-right classes. These classes apply the CSS float property to the image, making it float to the left or right side of the container.

Example: Float Left and Right

<img src="image.jpg" class="float-left" alt="Left Aligned Image">
<img src="image.jpg" class="float-right" alt="Right Aligned Image">

When using floating classes, make sure to clear the floats to avoid layout issues. You can use the .clearfix class on the container element or add a clearing element after the floated images.

To center an image horizontally within its container, you can use a combination of the .mx-auto and .d-block classes. The .mx-auto class sets the left and right margins to auto, while the .d-block class sets the display property to block, allowing the margins to take effect.

Example: Center an Image

<img src="image.jpg" class="mx-auto d-block" alt="Centered Image">

By applying .mx-auto and .d-block together, the image will be centered horizontally within its container.

You can also combine alignment classes with other Bootstrap classes, such as .img-fluid for responsive images or .rounded for rounded corners, to get the image look and alignment you want.

Example: Float Left with Rounded Corners

<img src="image.jpg" class="float-left rounded" alt="Left Aligned Rounded Image">

Remember to consider the layout and responsiveness of your design when aligning images. Test your code on different screen sizes to make sure the alignment works well and doesn't break the layout.

By using Bootstrap's alignment classes, you can easily control the positioning of images within their containers without writing custom CSS. This makes your code more readable and maintainable.

Image Overlays

Bootstrap lets you make image overlays by putting text and other content on top of an image. This is useful for adding captions, titles, or more information to an image. To make an image overlay, you can use the .card and .card-img-overlay classes together.

First, wrap your image and overlay content in a <div> element with the .card class. This makes a content container with default styling.

Next, add your image inside the .card container using the <img> tag. You can add more classes to the image, such as .card-img or .card-img-top, to make it fill the card container.

Then, add another <div> element with the .card-img-overlay class after the image. Inside this overlay container, you can add text, headings, buttons, or any other content you want to show on top of the image.

Example: Basic Image Overlay

<div class="card">
  <img src="image.jpg" class="card-img" alt="Image">
  <div class="card-img-overlay">
    <h5 class="card-title">Image Title</h5>
    <p class="card-text">This is an image overlay with text.</p>
    <a href="#" class="btn btn-primary">Learn More</a>

In the example above, the .card-title, .card-text, and .btn classes style the overlay content. You can change the text color, background color, and position of the overlay content using custom CSS or more Bootstrap utility classes.

When making image overlays, it's important to think about how easy it is to read the overlay text. If the image has a light background, use dark text colors for better contrast. If the image has a dark background, use light text colors. You can also add a semi-transparent background color to the overlay container to make the text easier to see.

Example: Image Overlay with Dark Background

<div class="card">
  <img src="image.jpg" class="card-img" alt="Image">
  <div class="card-img-overlay bg-dark text-white">
    <h5 class="card-title">Image Title</h5>
    <p class="card-text">This overlay has a dark semi-transparent background.</p>

The .bg-dark class adds a dark background color to the overlay container, while the .text-white class sets the text color to white for better contrast.

Image overlays can be a great way to add extra information or interactivity to your images. They can be used for different purposes, such as showing products, highlighting key features, or providing image captions.

By using Bootstrap's .card and .card-img-overlay classes, you can quickly make image overlays that look good without complex CSS. Try different content, styles, and layouts to find the best design for your specific use case.

Lazy Loading Images

Lazy loading is a technique used to improve website performance by loading images only when they are needed, rather than loading all images at once when the page loads. This can reduce the initial page load time and save bandwidth, especially for websites with many images.

To implement lazy loading for images in Bootstrap, you can use the data-src attribute instead of the regular src attribute in your <img> tags. The data-src attribute holds the actual image URL, while the src attribute can be left empty or set to a placeholder image.

Example: Using data-src attribute for Lazy Loading

<img data-src="image.jpg" class="img-fluid" alt="Lazy Loaded Image">

When the page loads, the images with the data-src attribute will not be loaded immediately. To trigger the loading of these images, you need to use JavaScript to detect when the images are in the viewport (visible area of the webpage) and then replace the data-src attribute with the src attribute.

Example: JavaScript code for Lazy Loading

document.addEventListener("DOMContentLoaded", function() {
  var lazyImages = []"img[data-src]"));

  if ("IntersectionObserver" in window) {
    let lazyImageObserver = new IntersectionObserver(function(entries, observer) {
      entries.forEach(function(entry) {
        if (entry.isIntersecting) {
          let lazyImage =;
          lazyImage.src = lazyImage.dataset.src;

    lazyImages.forEach(function(lazyImage) {
  } else {
    // Fallback for browsers that don't support IntersectionObserver
    lazyImages.forEach(function(lazyImage) {
      lazyImage.src = lazyImage.dataset.src;

The JavaScript code above uses the IntersectionObserver API to detect when images with the data-src attribute are in the viewport. When an image becomes visible, the data-src attribute is replaced with the src attribute, triggering the image to load.

For browsers that don't support the IntersectionObserver API, a fallback mechanism is provided to load all images at once.

To use lazy loading with Bootstrap, you can combine the data-src attribute with Bootstrap's image classes like .img-fluid to ensure responsiveness and proper styling.

By implementing lazy loading for images, you can improve your website's performance by reducing the initial load time and saving bandwidth. This is useful for websites with a large number of images or when targeting users with slower internet connections.

Keep in mind that while lazy loading can enhance performance, it may not be necessary for all websites or all images. Consider the specific requirements and characteristics of your website before implementing lazy loading techniques.

Responsive Embeds

Bootstrap has a class called .embed-responsive that lets you embed videos, slideshows, and other media in a responsive way. This class helps keep the aspect ratio of the embedded media, so it scales correctly on different screen sizes.

To create a responsive embed, first add a <div> element with the .embed-responsive class. Then, inside the <div>, add an <iframe>, <embed>, <video>, or <object> element with the .embed-responsive-item class.

Example: HTML code

<div class="embed-responsive embed-responsive-16by9">
  <iframe class="embed-responsive-item" src="" allowfullscreen></iframe>

The .embed-responsive-16by9 class is used together with .embed-responsive to set the aspect ratio of the embedded video to 16:9. Bootstrap has other aspect ratio classes like .embed-responsive-4by3 for a 4:3 aspect ratio and .embed-responsive-1by1 for a 1:1 square aspect ratio.

By using the .embed-responsive class and the right aspect ratio class, Bootstrap will automatically change the height of the embedded media based on its width. This means that the video or slideshow will scale proportionally and keep its aspect ratio as the browser window is resized.

When embedding media from external sources like YouTube or Vimeo, use the correct embed URL and include any necessary parameters. For example, you can add the allowfullscreen attribute to let users view the video in full-screen mode.

Example: HTML code

<div class="embed-responsive embed-responsive-4by3">
  <iframe class="embed-responsive-item" src="slideshow.html"></iframe>

A responsive slideshow is embedded using an <iframe> element. The .embed-responsive-4by3 class is used to set the aspect ratio to 4:3.

By using Bootstrap's .embed-responsive class, you can create responsive embeds for various types of media content. This helps make sure that your embedded media looks good and works well across different devices and screen sizes.

Remember to test your responsive embeds on multiple devices and browsers to make sure they work as expected. If needed, you can combine the .embed-responsive class with other Bootstrap classes or custom CSS to style and customize the look of your embeds.

Styling Images with Bootstrap

Bootstrap has classes that let you add borders, padding, and margins to images. You can also create your own CSS classes to change the look of your images.

To add a border to an image, use the .border class. This class adds a solid, thin border around the image.

Example: Adding Border to an Image

<img src="image.jpg" class="img-fluid border" alt="Image with Border">

You can change the border style by using classes like .border-secondary, .border-success, or .border-danger. These classes add colored borders to the image.

To add padding around an image, use the .p-* classes, where * can be replaced with a size value from 0 to 5. For example, .p-3 adds a padding of 1rem (16px) on all sides of the image.

Example: Adding Padding to an Image

<img src="image.jpg" class="img-fluid p-3" alt="Image with Padding">

Margin classes work the same way as padding classes. Use .m-* to add margins on all sides, or use .mt-* (top), .mr-* (right), .mb-* (bottom), or .ml-* (left) to add margins to specific sides of the image.

Example: Adding Margin to an Image

<img src="image.jpg" class="img-fluid mt-3 mb-3" alt="Image with Margin">

In addition to using Bootstrap's built-in classes, you can make your own CSS classes to style images. This gives you more control over how your images look.

Example: Custom CSS Class for Images

<img src="image.jpg" class="img-fluid custom-image" alt="Image with Custom Style">
.custom-image {
  border: 5px solid #f8f9fa;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.2);
  transition: transform 0.3s;

.custom-image:hover {
  transform: scale(1.05);

In this example, the .custom-image class is applied to the image element. The CSS rules for this class add a thick, light gray border, rounded corners, a box shadow, and a hover effect that slightly scales the image on mouse hover.

You can use CSS to change many other things about your images, such as opacity, filters, animations, and more. By combining Bootstrap classes with your own CSS, you can create image styles that fit your website's design.

Remember to keep your styles responsive and test them on different devices to make sure they look good at all screen sizes. You can use Bootstrap's responsive classes and media queries in your CSS to modify styles based on the viewport width.