Bootstrap 5.3 introduces several key differences compared to previous versions, particularly when compared to Bootstrap 4 and earlier. Here are some of the most significant changes:

1. JavaScript Framework

• Bootstrap 5.3 and 5.x: These versions have moved away from jQuery, using vanilla JavaScript instead. This change makes Bootstrap lighter and more modern, improving performance and compatibility with modern browsers.

• Previous Versions (3 & 4): These versions relied heavily on jQuery for interactive components.

2. Grid System and Layout

• Bootstrap 5.3: Utilizes Flexbox for layout management, providing a more flexible and responsive grid system. This allows for easier customization and better support for modern web design patterns.

• Previous Versions: While also responsive, earlier versions did not leverage Flexbox as extensively.

3. Customization and Theming

• Bootstrap 5.3: Offers enhanced customization options through Sass variables and CSS custom properties. This includes support for multiple color modes (e.g., dark mode) and improved theming capabilities.

• Previous Versions: While customizable, they did not offer the same level of flexibility in terms of color modes and CSS variables.

4. Components and Utilities

• Bootstrap 5.3: Includes new and updated components like offcanvas with responsive variations, improved alert and list group styling via CSS variables, and additional utility classes for better layout control.

• Previous Versions: Had fewer utility classes and less emphasis on CSS variables for component styling.

5. Accessibility and Compatibility

• Bootstrap 5.3: Places a strong emphasis on accessibility with improved support for screen readers and better handling of aria attributes. It also supports modern browsers but does not support older browsers like Internet Explorer 11 and below.

• Previous Versions: While accessible, they may not have had the same level of focus on modern accessibility standards.

6. Modular Structure

• Bootstrap 5.3: Offers a modular structure that allows developers to include only the components they need, reducing the overall file size and improving performance.

• Previous Versions: While modular to some extent, they did not offer the same level of granularity in component inclusion.

7. Icons and Assets

• Bootstrap 5.3: Includes Bootstrap Icons, a set of customizable SVG icons that can be easily integrated into projects without relying on external libraries.

• Previous Versions: Did not include a built-in icon set.

Overall, Bootstrap 5.3 represents a significant evolution in terms of performance, customization, and accessibility compared to previous versions.