Difference Between Bootstrap 3 And 4: What Is New?

Most developers have been going for the Bootstrap framework for many years, possibly for a good reason. The open-source developer’s framework has been helping website designers and the front-end website developers to make highly responsive and great-looking modern websites. People who use the fascinating framework are able to access the basic structures of both HTML and CSS in addition to the predefined classes. That, in turn, helps them improve their website’s responsiveness.  Bootstrap framework is available in various versions.

However, Boostrap 3, which entered the market in the year 2013 and the Boostrap 4 released in the year 2017 have been the most popular choices. If you are unfamiliar with the framework, then you are likely to find it hard to decide the one to select for your projects. That is the main reason we have come up with a list of the key differences between bootstrap 4 vs 3. The list should help you make an informed decision.

The Flexbox

Flexbox is among the crucial features that come with the Bootstrap 4 framework and the Bootstrap 3 framework. With this feature, you will be able to change the size of each grid column and manage the layouts alignment. Moreover, you will manage to navigate all components and change the formation of complex layouts easily. Initially, Bootstrap 3 used floats to carry out the tasks, but the Flexible Box Layout (Flexbox) made it easier to make deign flexible responsive layouts without the need for float or positioning.

Website designers and developers who rely on Flexbox can handle several tasks easily. Some of the things you can do with the Flexbox are:

  • Creation of grid columns of equal width
  • Design of cards that have equal height and width
  • Addition of auto margins for easier spacing
  • Development of utility classes to alter direction, alignment, scaling and display easily
  • Create a justified button and navigation group

The Bootstrap 3 contains four grid classes named as col-xs-3, col-md-3, col-sm-3, and col-lg-3. The most recent version of this open-source framework is the Bootstrap 4 that features five separate grid classes. The classes are .col-, .col-sm-3, .col-lg-3, .col-md-3 and col-xl-3. You should keep in mind that the Bootstrap 4 eliminated xs from the low breakpoint.

The new class is a new breakpoint that offers better support for the small devices, especially those with a size below 576px. In other words, your website will run properly on any device, including those with the smallest screen due to the XS class.


Bootstrap Navbar is written solely in the flexbox of the most recent version. It incorporates the use of most flexbox utilities as a way of improving customization and responsiveness of the layout. Here are some of the changes you should expect in the Bootstrap 3 Navbar.

  • Use of .nav base class is inexistent. That means you should only expect .navbar-nav class that is important for future projects.
  • The developer updated the .navbar-toggler to the new .navbar-toggler-icon to facilitate customization.
  • The .navbar-toggle class was changed to .navbar-toggler.
  • The Bootstrap 4 Navbar offers many preset colour options.
  • Users benefit from class .form-inline and not the .navbar-form class.

SAAS and not LESS

The developer updated the CSS source file from LESS to SAAS, and that makes another huge difference between Bootstrap 3 and the Bootstrap 4 framework. Perhaps, you did not know that SAAS is more powerful compared to the LESS and has many important functionalities like nested media queries, extend, mixing, rem, loops, em, and logical operators. Even though LESS is easier to learn and beginners will need a few weeks to be comfortable with SAAS, SAAS comes with many options when it comes to compiling SAAS to CSS.

Relative CSS units

One of the best topography practice and most popular on the web involves incorporation of relative units of em, px, and rem. The use of rem in place of px in the Bootstrap framework might come as a great surprise considering that the former was more flexible than the latter. Web developers who opt for rem are able to scale various elements up or down without worrying about getting stuck in any fixed size. That, in turn, helps them adjust the design of their websites easily and make them more responsive. Bootstrap 4 framework uses pixels for the width of containers and grid breakpoints in addition to media queries because the type of size does not affect the viewports.

Cards in place of panels, wells, and thumbnails

Bootstrap 4 framework replaced wells, panels, and thumbnails with cards. Cards work as thumbnails but are more flexible and can support various types of content. Therefore, users cannot .panel, .well, and .thumbnail classes. They will find .card-block, card and other modifier classes. And because cards are created with flexbox, aligning them is easier. In fact, developers can use the Bootstrap 4 framework to make cards of the same height. Cards are also informative, catchy and they facilitate categorization of information.

Dropped IE8 and IE9 support

Bootstrap 3 framework supported IE8 and IE9. As a designer or developer, the fact that Bootstrap 4 dropped the support will surprise you. On the upside, Bootstrap 4 framework supports iOS 7+ and IE9+ meaning that it has dropped the support for any earlier version. If you wish to keep any of the browsers, you will have to continue using the Bootstrap 3 framework.

Tooltips and popovers

Bootstrap 4 framework comes with a third-party library, known as the tether. The excellent library is only usable when positioning any related components on the webpages. If you need a tool that can help you improve the auto-placement of popovers and tooltips, you should not look anymore because the tether is a better choice.  Thousands of developers have named the tether to feature a Javascript library. You will have to include the tether in your HTML file.

Variable customization

The developer included every variable that you will use with the Bootstrap 4 framework in a file known as _variable.scss. You can also copy the variables to another file known as _custom.scss so that you can change the variable values or remove the default tags. In this case, you will just need to update one variable.

The utility classes

Utility classes help the users to arrange components faster and easily without having to change the layout. Bootstrap 4 utility classes are different from those of the Bootstrap 3 and the Bootstrap 4 framework has more utility classes. Utility classes considerably improve the project’s development time. For example, you can add responsive-friendly margin or padding values to one element with spacing utilities. With the utilities, users can manage sizing, alignment, and layout easily. The user can change or block the alignment of the site’s elements.

Bottom line of bootstrap 3 vs 4

The most recent Bootstrap framework version has many improvements and changes in typography, styles, and layouts. The updated and launched features and tools will help you design your websites flawlessly.

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