Bootstrap Interview Questions and Answers (Updated to latest Bootstrap 5)

World Wide Web has tremendously changed over the last decade with new modern designs and languages further laying the path for future internet websites. If we focus solely on web designing, Bootstrap is one of the main standalone front-end frameworks which has vast contribution in terms of website development and global acceptance. Responsive web designing which has taken the internet world by storm is now synonymous with ‘Bootstrap’. It is one of the most used responsive frameworks and is used all over the world for its ease of web designing which is responsive completely.

Top Bootstrap Interview Questions and Answers
Top Bootstrap Interview Questions and Answers

The latest version Bootstrap 5 offers more features and changes that you should know.

Here is a simple glimpse of changes from Bootstrap 3 vs 4 vs 5

NoBootstrap 3Bootstrap 4Bootstrap 5
Release DatesJanuary 2018May 2021 
Grid Levelsfive Grid levels: xs, sm, md, lg, and xl.six Grid levels: xs, sm, md, lg, xl, and xxl.
Jquery/JSincludes jquery and all associated plug-insreplaced with vanilla JS and several functional plug-ins
Comptabilitycompatible with both Internet Explorer 10 and 11does not support Internet Explorer 10 and 11
ColumnsColumns can be positioned relative to one another.Columns cannot be positioned relative to one another.

If you are going for an interview in this CSS-based framework then you should read these mentioned questions and answers. These are created with in-depth understanding core fundamentals of Bootstrap in mind.

Also Check out special section for Bootstrap Experienced below:

  • Q1. What are the different ways of using Bootstrap?
  • A1. Bootstrap offers compiled and minified CSS with JavaScript & fonts. You can download the latest version from their official Bootstrap website. There is also CDN support for Bootstrap at
    <!-- Latest compiled and minified CSS --> <link rel="stylesheet" href="" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

    Source Code that can be used with LESS and SASS is also available. It also has completely CDN support with direct URL’s that once implemented runs the Bootstrap directly for your website. Bootstrap is open source and can also easily install it with Bower, npm, Composer.

  • Q2. Explain the basic structure of the Bootstrap framework!
  • A2. The bootstrap framework makes use of the front end only. Its overview starts with HTML5 based grid system i.e. 12 column layout for responsive web design which has a mobile-first design approach. Than typography concerns text formatting support for LESS and SASS in the future. Making Bootstrap tables is easy too whereas Bootstrap Forms are very popular.
    Ease of style and making define the Bootstrap buttons with default classes available for images as well. Comprehensive helper classes and responsive utilities are there which caters to ad hoc functionality in web designing if required. For added functionality, you need to download Jquery plugins i.e. Bootstrap Modals, Bootstrap Tooltip, etc.

  • Q3. What are Bootstrap Grids? Explain different types of bootstrap grids in brief!
  • A3. Bootstrap grids are the popular 12 column based grid system for responsive web layouts.
    Fixed Layout is when some portion like header are fixed and don’t adjust to different browser but still are responsive.
    Fluid Layout is completely dependent on the browser and adjusts according to the device width. Bootstrap uses 1170x as standard grid layout for default.

  • Q4. Does Bootstrap supports LESS and SASS CSS structure in any form?
  • A4. Bootstrap current version 3.0 fully supports LESS bases web development but for future Bootstrap 4.0 alpha version uses SASS so it Bootstrap will become comprehensive CSS based framework with LESS and SASS support.

  • Q5. Does Bootstrap Supports all the Modern Browsers?
  • A5. Current version i.e. Bootstrap 4 supports all the modern browsers with latest version i.e. Firefox, Google Chrome, IE (Internet Explorer), Opera and Safari

  • Q6. Popular term ‘Mobile First design’ was introduced in Bootstrap from beginning?
  • A6. Although Bootstrap started supporting responsive web designing from version 2.0. Mobile First design was introduced in the Bootstrap current version 3.0

  • Q7. Explain the use of media queries in the Bootstrap Framework!
  • A7. Three main breakpoints are used in Bootstrap for making it compatible with all platforms.
    1. Small Devices (Mobiles, Smartphone, Tablets,) at 768px
    2. Medium Devices (PC, Desktop, Laptops) at 992px and up
    3. Large Devices (Large Screen desktops, Laptops) with 1200px and up

    Max-width and Min-width are used in CSS media queries for affecting the specific device set.

  • Q8. Explain the use of icons in Bootstrap Framework!
  • A8. There are around  250 glyphs available free of cost with Bootstrap from Glyphicon Halflings fonts set. You can select the best one from the given set of icons easily.

  • Q9. What is the default Gutter width provided in the Bootstrap 3 Grid System?
  • A9. 30px is the standard size given to all Grid layouts in Bootstrap 3 by default (15px on each side of a column). But Now in Bootstrap there are no pre-defined Gutters, you can assign custom values

  • Q10. What if there are more than 12 column being used in the Bootstrap grid system? Does it still work?
  • A10. Yes it does work and restructures the columns accordingly. each group of extra columns acts as one unit, wrap onto a new line

  • Q11. What are the default sizes given to <body> tag in the Bootstrap Framework?
  • A11. In this framework default font size : 14px and line height 1.428 px is given to <body> tag. Also <P> tag are given padding-bottom of 10px by deault.

  • Q12. Explain in brief about Bootstrap 3 Tables!
  • A12. Tables can be easily made with basic html tag and specific classes provided in Bootstrap 3. You can make table with Striped rows, bordered table, hover rows, condensed table and responsive table using their specific classes for right results. Read more about Bootstrap 3 tables here.

  • Q13. Bootstrap multiple form types i.e. horizontal, inline and basic have similar views when they are viewed under 768px devices? Yes or No Explain!
  • A13. Yes different types of Bootstrap forms when viewed under 768px devices render similar properties. Inline form only works at device viewports that are at least 768px wide

  • Q14. What are Offsetting columns in Bootstrap 3 Grid System?
  • A14. Using Offsetting columns you can easily push the column to create more spaces between your content. Just add them to your particular classes with same suffix i.e. .col-md-offset-*. Although .col-xs classes don’t support offset but they are customized using empty cells only.

  • Q15. Can we make images responsive in Bootstrap?
  • A15. Yes we can make images responsive by adding class .img-responsive which in turn applies CSS properties with max-width(100%)  as well as height (auto) for covering parent element.

  • Q16. What is well class in Bootstrap? What it does?
  • A16. Using Well class to any Bootstrap container results in to sunken text or inset affect to the container element and you can add small (.well-sm) & large classes (.well-lg) to make it more effective. Find more relevant information here on Bootstrap Well

  • Q17. Can we customize columns default settings to create complete custom layout from scratch in Bootstrap?
  • A17. Yes there are options in Bootstrap 3 with comprehensive custom layout

  • Q18. What are Contextual colors in Bootstrap 3?
  • A18. These are basic colors provided them in this CSS framework. You can use them with buttons, inputs, text as well as background too!

  • Q19. What are input groups and Button Groups in Bootstrap 3 Framework?
  • A19. Using these groups you can stack them together and their behaviour is controlled easily with parent element.

  • Q20. What is Bootlint?
  • A20. It is the official Bootstrap HTML linter tool. Bootlint is used to check the HTML mistakes that comes along in the structure that you have made for your web page

Bootstrap 3 Interview Questions and Answers for Experienced

  • Q. What is Jumbotron in Bootstrap? Explain its use!
  • A. A Jumbotron is a lightweight, flexible component in Bootstrap to highlight special information in different view to the users respectively.

  • Q. What are bootstrap modals? Explain its use?
  • A. There are dialog box/popup window that appears over the whole page content. This is part of the modern invention that has become popular with major websites using them for showing special offers, query form, videos and more with Bootstrap.

  • Q. What are bootstrap Panels and their use?
  • A. Bootstrap Panels are another flexible component that comes with bordered box and extra padding around its content. They can used almost any section of the web page header, footer body, list group and more!

  • Q. What is Bootstrap tooltip?
  • A. Bootstrap Tooltip plugin is small pop-up box that appears when user moves over the element.

  • Q. What is Bootstrap popover?
  • A. Bootstrap popover are popu-up boxes that appear over the element when user cilck on the specified elements.

  • Q. Differentiate between col-lg-* , col-md-* and col-sm-* in Bootstrap?
  • A. These are the standards breakpoints in Bootstrap Grid system on which the whole framework in based upon.

  • Q. How to Vertical Align in bootstrap?
  • A. With Bootstrap latest version vertical alignment is given special classes that you can use in the HTML code easily i.e. .align-baseline, .align-top, .align-middle, .align-bottom, .align-text-bottom, and .align-text-top
Vertical Alignment is effected with inline, inline-block, inline-table and table cell elements respectively.

  • Q. How to center a column in Bootstrap?
  • A. You might be encouraged to apply custom CSS to center the column in Bootstrap but also there are few hacks available.
Method 1: Adjust offset equal to half of the remaining size of the row
Method 2: By Combination of float and margin

  • Q. Explain the use of Bootstrap Scrollspy Plugin in short!
  • A. This Scrollspy plugin is used to automatically update links in the navigation list based on the scroll position. Quite popular Bootstrap designing plugin uses complex CSS structure and JS script.

  • Q. What is page header class in bootstrap?
  • A. .page-header is specific set to highlight the top header section of the page. It combines with h1 HTML with small element for heading and sub-heading respectively.

Bootstrap 4 Interview and Questions Answers

  • Q. When did Bootstrap 4 Come into Existence?
  • A. First Stable version was introduced on January 18, 2018, after alpha and beta versions.

  • Q. What is the minimum browser support for this Bootstrap 4 Version?
  • A. IE 10+, iOS+7, and official support for Android v5.0 Lollipop’s Browser along with WebView is now there with Bootstrap 4. For older versions, one needs to work with Bootstrap 3+. All latest versions of Google Chrome, Firefox, Internet Explorer, Opera, and Safari (except on Windows) have the support for Bootstrap.

  • Q. What are Bootstrap 4 Cards?
  • A. These are newly adopted components that are highly mobile in design and provide effective way to represent data in searchable form. For more information read all about here Bootstrap 4 Cards Examples.

  • Q. Are there any specific CSS behavior or type changes in Bootstrap?
  • A. Yes, CSS has been switched from LESS to SASS, px to rem for primary CSS units, Global fonts has also increased from 14px to 16px, the fifth tier for grids at 576px breakpoints, many small changes and use of Bootstrap in the non-responsive web is not supported from this latest bootstrap 4 version. CSS Flexbox is enabled by default to move away from float behaviors.

  • Q. Which major components are dropped in Bootstrap 4 from Bootstrap 3?
  • A. These are the main changes in the Bootstrap 4 with respect to its last framework
  • 1. Wells, Thumbnails, pager, label and panels have been completely removed with the use of better mobile styles bootstrap cards.
  • 2. Affix Jquery Plugins has been dropped too.
  • 3. Global Glyphicons Icon Font are dropped with new version of Glyphicons, Octicons, Font Awesome and other alternatives can be used.
  • 4. New grid breakpoint at 576px as sm are introduced.
  • 5. rem units have been introduced from em in all designing aspects.

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