Twitter Bootstrap 4 Complete Reference for Beginners

Twitter Bootstrap 4 is a popular front-end framework that makes building responsive websites a breeze. It's a set of pre-designed HTML and CSS templates that save you time and effort.

Bootstrap 4 is built on the latest version of CSS, which means it's faster and more efficient than its predecessor. This is especially noticeable when it comes to loading times, which can be a major issue for websites that rely on heavy graphics or animations.

One of the most significant changes in Bootstrap 4 is the introduction of a new grid system. This allows you to create responsive layouts that adapt to different screen sizes and devices. You can use a 12-column grid to create complex layouts that are easy to maintain and update.

With Bootstrap 4, you can create a wide range of responsive components, including navigation bars, buttons, and forms. These components are all customizable, so you can tailor them to fit your specific needs.

Bootstrap 4 makes it easy to create a basic layout with its grid system, which is based on 16 foundational columns. This allows for a wide range of variations and combinations.

You can create a basic layout with two columns, each spanning a number of the 16 foundational columns.

To add some flair to your text, Bootstrap 4 offers a variety of utility classes, including font-weight classes, such as font-weight-bold and font-weight-light, and text decoration classes, like text-decoration-none.

Bootstrap is tested and supported in major modern browsers, making it a reliable choice for developers. This includes the latest versions of Safari, Google Chrome, and Firefox.

The latest Safari version is fully supported, so you don't have to worry about compatibility issues.

Firefox 4 and above are also supported, ensuring a smooth experience for users.

Internet Explorer 7 and above are supported, which is good news for developers who still need to cater to older browsers.

Opera 11 is also supported, providing a wide range of options for developers to choose from.

Here's a quick rundown of the supported browsers:

Utility Classes for Spacing are a game-changer for developers. They allow you to quickly change paddings and margins on your site.

The syntax for these classes is straightforward, using the m- prefix for margins and p- prefix for paddings. For example, adding the .m-a-0 class sets margins to 0 on all sides of an element.

You can use these classes to easily add space between elements or change the padding of a container. It's a huge time-saver and makes coding a lot more efficient.

Some of the new spacing utility classes include m-a-0, m-a-1, m-a-2, and m-a-3 for margins, and p-a-0, p-a-1, p-a-2, and p-a-3 for paddings.

Here's a breakdown of the new spacing utility classes:

These classes are a great addition to Bootstrap 4 and make it easier to create responsive and well-designed websites.

Customizing Bootstrap is a breeze, especially with the new streamlined variable customization feature. This allows you to change default values by simply copying settings from the _variables.scss file into another file called _custom.scss.

You can customize many things, such as colors, spacing, link styles, typography, tables, grid breakpoints, and containers. The grid system, for instance, can be modified to have up to 24 columns, which is a great way to give your project more flexibility.

To customize the grid, you'll need to change the three @grid-* variables and recompile the Less files. This will allow you to create a unique layout that suits your project's needs.

Using a CDN like jsDelivr can be a game-changer for your website's loading time. Many users already have Bootstrap 4 downloaded from jsDelivr when visiting another site, which means it will be loaded from cache when they visit your site.

This leads to faster loading times, and most CDNs will also serve the file from the server closest to the user, further reducing load times.

If you're using the CSS part of Bootstrap, you don't need jQuery and Popper.js. However, if you're using Bootstrap's JavaScript components, like modals, tooltips, and popovers, you'll need these libraries.

Here are some Bootstrap components that require jQuery and Popper.js: Closable alertsDropdownsModalsTooltips and popovers

You can customize Bootstrap's grid system to suit your needs by modifying the three @grid-* variables and recompiling the Less files.

This means changing the default 16-column grid to a 24-column grid, which is the maximum number of columns Bootstrap can handle.

To achieve this, you'll need to update the @grid-columns, @grid-gutter-width, and @grid-row-width variables in your Less files.

Here's a summary of the variables you'll need to update:

Once you've updated these variables, simply recompile your Less files to apply the changes to your grid system.

With Bootstrap's grid system customizable to your needs, you can create a responsive and flexible layout for your web application.

Compiling Less is a crucial step in the customization process. You'll need to recompile .less files in /lib/ to regenerate the bootstrap-*.*.*.css and bootstrap-*.*.*.min.css files.

If you're modifying .less files, recompilation is a must. This ensures that your changes are reflected in the generated CSS files.

When submitting a pull request to GitHub, recompilation is not optional. You must always recompile to ensure that your changes are properly reflected in the code.

Button Modifiers can greatly enhance the user experience by adding visual cues and interactive elements to your buttons. You can use the .btn-lg class to make buttons larger, perfect for calls-to-action on mobile devices.

For a more subtle approach, the .btn-sm class can be used to make buttons smaller. This is ideal for situations where you want to group multiple buttons together.

You can also use the .btn-block class to make buttons span the full width of their container. This is particularly useful for buttons that need to stand out on a page.

To indicate that a button is currently active, you can add the active class to it. This is a great way to provide feedback to the user about their actions.

On the other hand, the disabled class can be used to indicate that a button is currently unavailable. This is a crucial feature for accessibility and preventing accidental clicks.

In some cases, you may want to use a checkbox or radio button as a button. Fortunately, you can achieve this by applying the checkbox as button or radio as button modifier classes.

Here's a summary of the button modifier classes:

Bootstrap 4 finally drops support for Internet Explorer 8, allowing them to convert to relative CSS units.

This means they're using REMs and EMs instead of pixels, which makes it possible to implement responsive typography on Bootstrap sites.

Relative units increase readability and make sites more accessible for disabled users.

You can try out relative units with the new Bootstrap 4 on Codepen to see how they work.

Bootstrap 4 offers a flexible way to implement a fluid layout, but it's not the default choice due to Internet Explorer 9's lack of support for the flexbox module.

Flexbox is a powerful layout system that can be used in responsive design, providing a flexible container that expands or shrinks to fill the available space.

The opt-in flexbox feature is only recommended if you don't need to provide support for IE9, as Bootstrap 4's default layout uses float and display CSS properties instead.

Here are some examples of how to use flexbox in Bootstrap 4:

To take advantage of flexbox, you can use classes like flex-*-column, flex-*-row, and flex-fill to create a flexible layout.

When you download the customization package, you'll find a well-organized directory structure that makes it easy to find what you need. The download includes compiled and minified variations of CSS and JS files.

You'll get both compiled CSS and JS files, which are useful for development, as well as compiled and minified versions that are perfect for production environments. These files are labeled as bootstrap.* and bootstrap.min.* respectively.

Source maps are included for use with certain browsers' developer tools, allowing you to easily debug your code. These source maps are available as bootstrap.*.map files.

Bundled JS files, such as bootstrap.bundle.js and minified bootstrap.bundle.min.js, are also included in the download. These files include Popper, which is a useful library for creating interactive elements.

We use Semantic Versioning to maintain transparency and backward compatibility in Bootstrap.

Bootstrap is maintained under the Semantic Versioning guidelines to ensure we follow a consistent release cycle.

You can find changelogs for each release version of Bootstrap in the Releases section of our GitHub project.

Release announcement posts on the official Bootstrap blog contain summaries of the most noteworthy changes made in each release.

Forms and Inputs can be customized to fit your needs with Twitter Bootstrap 4. You can change the size of form inputs, selects, and textareas by adding classes like .form-control-lg or .form-control-sm.

To create a form, you can use the form-group class, or go for a more grid-based approach. If you want to make your form more compact, use the form-inline class. Alternatively, you can use the form-control class for a more standard form input.

Here are some common form classes:

You can also use input groups to add some extra functionality to your form inputs. This can include input-group-prepend, input-group-append, and input-group-sm or input-group-lg for different sizes.

Forms are a crucial part of any website or application, and Bootstrap provides a wide range of tools to help you create them. You can choose from several form classes, including form-group, form-inline, and form using the grid.

One of the most common form classes is form-group, which is used to group form elements together. You can also use form-inline to create a horizontal layout for your forms. If you want to create a form that uses the grid system, you can use the form class with the grid classes.

Bootstrap also provides several form control classes, including form-control, form-control-lg, and form-control-sm. These classes allow you to customize the size of your form inputs. For example, you can use form-control-lg to create a large form input or form-control-sm to create a small form input.

Here are some common form control classes:

You can also use form-check and form-check-inline to create checkboxes and radio buttons. Additionally, you can use disabled items and readonly to create read-only form fields.

The disabled state is crucial for buttons that aren't active or are disabled by the app. For links, use the .disabled class.

If a button is disabled, it's best to use the :disabled pseudo-class. This helps users understand that the button isn't clickable.

Javascript is necessary for more complex forms, but don't worry, we've got you covered with plugins that make it easy to integrate with Bootstrap.

For the basics, you can get started with a lightweight option, but if you need more information or want to see some live demos, check out the plugin documentation page.

If you're feeling overwhelmed by the options, you might want to take a look at the 10 Lightweight Alternatives To Bootstrap & Foundation, which can help you choose the perfect framework for your project.