Top 25+ Web Developer Interview Questions and Answers

This tutorial provides a set of commonly asked Web Developer Interview Questions and Answers for junior and senior-level front end web developers:

It is essential for the marketing team to build a reliable web presence, advertise their products and services to their prospective customers, keep track, and provide after-sales services to existing customers.

Web applications are built with the purpose of being accessible globally, being recognized, and offer their products and services across the international market.

Web Developer Interview Questions and Answers

For building web-based applications, it is mandatory to have in-depth knowledge of markup languages like HTML5, Cascading Style Sheet CSS3, JavaScript, and JS libraries for user interactions, for handling DOM elements, to validate client inputs, and to make dynamic and responsive web pages.

What Is Web Development

Web development refers to the work involved in building and maintaining websites and web-based applications like online eCommerce sites, Amazon, Flipkart, eBay, etc and Social Networking sites like Facebook, LinkedIn, Instagram and Twitter.

This also includes the work in building websites for railways, banks, all major government sites to broadcast information and generate awareness.

Generate public awareness and provide education via news channels using web conferencing software Skype, Zoom, GoToMeeting. Provide online entertainment through web series like Netflix, Amazon Prime, MX player, etc. Educate students, conduct meetings to address customers and teams across geographical boundaries.

Now let us move on to the most common Web Developer interview questions for junior as well as senior-level interviews.

Frequently Asked Web Developer Interview Questions

Q #1) Explain the functionality of a browser.

Answer: Browser offers various features. These are as follows:

  • It helps access HTML pages and all web elements used in web-based applications, as well as websites, and display responses from other sites as an answer to the requests.
  • Allows web search for the site of your interest by entering URL or web address in the address bar and view response by using any of the search engines.
  • Navigation controls are used for going back to recently opened pages by clicking the back button and next button to move forward.
  • History keeps track of the visited sites in chronological order. It allows remembering or bookmarking sites of your interest to refer or explore at a later stage. It also saves previously visited sites in the form of cache and make visitor recognized by sites, making access to those sites quicker.
  • Manages passwords for frequently used websites requiring authentication and in most cases keep users already logged into the account.
  • Allows accessing various sites, exchanging information via API calls, communication via email, data, and media file-sharing software.

Example of browsers: Internet Explorer, Mozilla Firefox, Google Chrome, Opera, Safari.

Q #2) Explain HTML 5, CSS3, JavaScript, and their importance in web development.


  • HTML is a platform and browser independent markup language with a series of tags that provide the structure for a web page.
  • CSS improves page layout and its contents with style.
  • JavaScript controls the behavior of web elements, and thereby makes your website interactive/responsive, validates user input values, capture website visitor’s information and recognize previous visitors, help in analyzing the percentage of blog post visitors click-through rate.

Q #3) What do you understand by Framework?

Answer: Framework is a structure that provides a platform to create applications. It is a collection of similar types of files placed in such a way that they are configured to connect/integrate with each other internally.

Example: API framework, that contains well tested, pre-written, and compiled classes to accomplish common functionalities like upload file feature, read file contents, reports in PDF and similar formats integrated with their web application.

Q #4) What is a library with context to web development?

Answer: A library is a collection of code that are pretested and designed for expected functionalities developed by developers and are available in repositories. Web developers can integrate these libraries and utilize their functionalities rather than reinventing the code to accomplish the same functionality from the beginning.

You can use iText and Apache FOP libraries in your application to help export your data in pdf format files.

Q #5) What are the reasons for the browser freeze issue?

Answer: To identify the root cause and to resolve the frequent browser freeze issue, follow the steps mentioned below:

Here, we are considering Google Chrome as the default browser.

  1. Check any issue related to the Internet: Click on Window icon (Start) -> Select Control Panel -> Under Network and Internet -> Click on View network status and tasks -> Check View your active network – click on connect or disconnect -> It should display Internet connection for the selected network.
  2. Chrome is not closed properly: On the extreme to down right corner, right-click and select start task manager, if you find multiple chrome.exe under processes tab, right-click on that record and select End process. This will free up RAM space. Then relaunch Chrome again.
  3. Disable Chrome Extensions: Open Chrome browser and type in the address bar -> chrome://extensions/ and press Enter. Disable all active extensions and restart the Chrome browser again. Go to Chrome extensions and enable all extensions.
  4. Scan computer for any malware: Launch Chrome and navigate to settings. Click on Advanced, find Reset, and Clean up. Click on Clean up computer.
  5. Reset Chrome settings: Launch Chrome, go to settings, click on Advanced, find Reset and clean up and click Restore settings to their original defaults.
  6. Remove Incompatible applications: During a scan, if Chrome detects any incompatible application, click on update or remove incompatible applications.
  7. Finally, if the issue still persists, uninstall the Chrome version, and install the latest version.

Q #6) How to improve the user experience for users visiting your website?

Answer: Following are the suggestions to improve the user experience:

  • Your website/application should be running 24×7.
  • It should handle multiple user access load during peak time or season.
  • It should be user friendly, and easy to navigate to the features that the visitor is looking for.
  • Should have engaging videos to introduce your product features.
  • The website should be searched from search engines based on keywords entered.
  • The website should be integrated with a payment gateway with all possible alternatives for transactions.
  • Should have free to use features available for users to decide on buying your product.
  • User data should be secured while accessing the website.
  • Sessions and cache features should recognize returning visitors.

Q #7) What are the video formats used in web development?

Answer: Some video formats supported and used in web development are listed below:

  • AVI by Microsoft
  • FLV Adobe flash video player
  • WMV supported by Windows media player
  • MOV by QuickTime player
  • MP4 supported by mobiles and other platforms

Q #8) How would you include accessibility features to your website?

Answer: Accessibility is an essential feature required to be implemented on your website to allow visitors with special needs, disabilities to access and explore your website.

  • The website should be keyboard friendly, i.e. all features should be accessible without the use of a mouse.
  • Users should be able to turn off dynamic and moving content such as GIF files, animations, video files. These contents may affect adversely to epileptic users.
  • Transcripts/captions for watching videos. For deaf users, watching a video with subtitles is not enough, features like captions should be displayed during the video run.
  • Voice assistance feature and tagging photos, graphics, and buttons for visually impaired visitors are essential to follow steps as directed to explore and use features offered in the website
  • Auto-complete features in the search bar and easy to find features for visitors with delayed or poor motor skills.
  • Increase the size of the clickable area. Use subtle colors for visitors having color blindness.

Q #9) When would you apply AJAX in your web application?

Answer: AJAX updates section of page contents, without reloading the entire page. This feature is essential when user needs fast results, without any delay of waiting for the request sent by clicking the submit button and waiting for the response. The server load can be reduced by applying AJAX with less number of requests which saves bandwidth.

You can use AJAX for form validation. Instead of pop-up windows, the lightbox can be used, sorting and filter the content in tabular format, displaying results or votes using the chat application, reloading captcha for authentication checks.

Q #10) How can we implement web services in web-based applications?

Answer: Web application sends requests to a web service using the HTTP protocol. At a given URL, the web service processes the request and returns the response back to the application. SOAP and RESTful are two types of web services.

Q #11) How and what security features can you apply to your website?

Answer: To guard your website against data theft, you need to improve security for your website, such as

  • Enforce strong password policy, allowing password to have at least 10 characters and should contain upper, lower, special characters and numerals.
  • Host that installs your website should have a backup facility, installed antivirus and firewall to secure your content.
  • The Login page should have Captcha, OTP features, block account feature( in event of entering 3 wrong passwords), etc. to prevent access to your account by unauthorized visitor.

Q #12) What configuration and setup is required for sending emails via your website?

Answer: Ideally you can configure your SMTP on a single server using a third-party service like Gmail SMTP, or use elastic email, using hostname, port, username, and password.

Q #13) What would you build a responsive website for?

Answer: Responsive web design help automatically resize the browser width and height based on desktops, tablets, and mobile with respect to desktop or laptop monitor size.

Q #14) What are the formats for data exchange?

Answer: Various data exchange formats are XML, CSV, JSON, and Text formats.

Q #15) What do you mean by protocol?

Answer: In networking terminology, the protocol is a set of rules to format and process data. In order to communicate, both devices should have the same protocol. Internet Protocol (IP) is a network layer protocol and is responsible for routing. Transmission Control Protocol (TCP) transfers packets of data across networks.

HyperText Transfer Protocol (HTTP) is a layer 7 used in the Internet and transfers data between devices. User Datagram Protocol (UDP) are used in fast data exchange applications like video streaming and gaming.

Q #16) What techniques would you apply to reduce page load time?

Answer: In order to reduce page load time and improve performance, the following techniques can be applied:

  • Apply latest versions of web building technologies like CSS3 and HTML5
  • Use JavaScript and Style Sheets to minimum
  • Try to avoid the use of Redirects
  • Use the small size of images
  • Include code from Content Delivery Network (CDN)
  • Apply AJAX for fast and responsive web applications

Q #17) List the differences between HTTP 1.1 and 2.0?

Answer: The differences between HTTP 1.1 and HTTP 2 are listed in the below table:

Request sent and responses received were in plain text format.Messages both request and response are encapsulated in binary format, giving more protection from any unauthorized alterations.
Finds difficulty in handling whitespace, capitalization and line endings.Use binary protocols that handle elements like whitespace, capitalization and line endings more efficiently
Needs more bandwidth to process the page contentsConsumes less bandwidth to display page contents
Prioritization of loading contents is not possible in HTTP 1.1Developers have control over prioritizing / uploading content in the order of their preference.
Loads resources one after another taking time to load the contents on a pageSends multiple streams of data using single TCP connection., resolving head-of-line blocking problem in HTTP 1.1
Metadata is transferred in plain text, hence need more overhead to handleUses header compression mechanism, that reduce overhead
HTTP 1.1 can handle only plain text, and is not compatible to process CSS, JavaScript, images, sounds, videos, and digitized smell, touch samples.Uses server push help to store resources to be used in request in browser's cache, even before requested, displaying content quickly.

Q #18) What priorities you would consider while building a web application?

Answer: The following priorities should be kept in mind while building web applications:

  • Web site pages should be tested for performance as it should load as quickly as possible.
  • Applications pages should not have any broken links.
  • The application should be compatible with all major browsers like Mozilla Firefox, Google Chrome, Internet Explorer and Opera.
  • The site should contain keywords that are accessible to search engines.
  • There should be seamless connectivity with the database.
  • Database entities such as stored procedures should be thoroughly tested with valid input.
  • Backend tables should be secured, tamper-proof.
  • Data insertion should be validated by constraints at column and row levels.
  • Inserting data into DB tables and viewing them in the user interface process should be as quickly as possible.
  • The framework being used to integrate pages should be simple and should be tested without any compilation.
  • User input pages should be designed with minimal inputs from the user, elements used should be user friendly to access.
  • Use of HTTP2 to load page content quickly.
  • The use of JavaScript should be minimum.
  • Accessibility provision such as a speaker to read the text, bigger font size, screen touch access should be provided so that people with physical limitations can also access the website with ease.
  • Should integrate media files like audio and video that can be opened without relying on local software to execute these files.
  • Web pages should be responsive to mobile screens.

Q #19) What are the new features introduced in HTML5?

Answer: New semantic, graphic, multimedia elements were introduced in HTML5, various attributes to elements were added whereas few elements were removed.

It added major new features such as multimedia elements video and audio, geolocation API, APIs on the web storage, web socket, JS web worker, Canvas and Drag-n-Drop were also introduced.

Q #20) Explain with examples, differences between Canvas and SVG.

Answer: Canvas and SVG both containers are used to store graphics in the HTML page, however, they have the following differences between them.

< svg > is a container element for graphics like box, circle, ellipse etc in HTML page< canvas > is container for drawing graphics using javascript
SVG is scalable and suitable for high resolution printingCanvas is not scalable and are not suitable for high resolution printing
Display better performance loading small number of objects and large surface objectsDisplay better performance loading large number of objects and small surface object
SVG can be modified by script and cssCanvas can be modified only with script
SVG is vector based made of shapesCanvas is raster based made of pixels

Q #21) What is the DOM element and its hierarchy?

Answer: Document object is an HTML document that gets displayed in a browser window when we access the web page. DOM or Document Object Model is the way this document is accessed or modified.

The window object is a parent of all the elements, followed by a Document object that displays page content, then comes the Form object, which is identified by <form> </form> tags.

Form control elements: All the input elements like text fields, buttons, radio buttons, checkboxes, lists, etc. are contained in the form object.

Q #22) When should you use id and class selector?

Answer: ID as a selector is defined to uniquely identify it as an element, hence there should not be same ID applied to any other element within the same page. Whereas class selectors are types of CSS selectors that are applied in order to add style to that element, for example, font family, font size, or color, hence class selectors can be applied to multiple elements.

In JavaScript we have getElementById() method that returns the first element found in source code, whereas getElementsByClassName() method returns collection of elements with particular classname.

Q #23) Explain APIs introduced by HTML5.

Answer: HTML 5 has introduced the following API methods:

  • High-Resolution Time API: It gives the current time in resolution to sub-millisecond, independent of system clock skew or adjustments.
  • User Timing API: This allows accurate measurement of JavaScript code performance.
  • Navigation Timing API: It helps in the assessment of time-lapse log during page load delays and takes account of page redirect, DNS lookup, and time to construct DOM, TCP connection delays, etc.
  • Network Information API: It helps identify web visitor’s connection type and status of the entire bandwidth log.
  • Vibration API: It can stimulate reaction during certain events in gaming applications by vibrating user devices (mobile phone) giving ultimate user experience.
  • Battery Status API: It offers information about device battery state such as charging, remaining seconds till it is fully discharged, etc.
  • Page Visibility API: It gives details about page visibility statuses like minimized, currently focused, providing decisions on stopping CPU or bandwidth consumptions.
  • Fullscreen API: It enables a full-screen display from the user based on the specification of the application.
  • getUserMedia API: It provides access to multimedia streams such as video, audio, or both embedded in a web page.
  • WebSocket API: It maintains a persistent connection between browser and server.
  • Geolocation API: This helps track the geographical location of the place and people via Global Positioning System (GPS) and retrieves latitude and longitude thereby plotting real-time position on the map.

Q #24) What is the difference between Null, Empty, and Undefined value and how can you handle each?

Answer: Empty string, Null, and Undefined are similar in type, but differ from each other.

Undefined: When we just declare a variable but have assigned no value. OR variable is not existent or not declared. Example: value; console.log(value); ==> undefined

Null: Identifiers or names given to functions, variables, does exist, but has no value. i.e. value is null.Example: val = null

Empty String: When a variable with the string data type does not contain any character data. Example: a =””;

Q #25) Explain different pop-up windows used in JavaScript.

Answer: There are mainly three types of pop up boxes in JavaScript, viz. Alert, Confirm, and Prompt.

Alert is a pop-up window to give information to the user with the Ok button. Users can read the message and click on the Ok button to close this window.

The syntax used for alert in JavaScript:


Confirm is a pop-up window for users to decide and select either one of the options, from OK and Cancel.

  • In order to agree with the message like Do you want to?, the user can click OK to confirm the decision.
  • In order to disagree with the message, the user can click Cancel and opt-out from the decision.

Prompt is a type of pop-up where the user is advised to enter some value like name, or age, and upon clicking the OK button, it accepts the value entered. Example: yourage = prompt(“Enter your valid age”);

Q #26) Describe the use of CSS animation with example.

Answer: You can add animation (gradually change from one style to another) to HTML elements without the use of JavaScript or Flash, using CSS animations.

Keyframes are specified that hold what styles the element will be changed at certain times.

An example is as given in the below screen:

CSS animation

CSS animation example change of color from red to aqua

Q #27) Explain the purpose of each of the HTTP request types supported by RESTful Web services

Answer: In RESTful web service, each HTTP request type has a specific purpose. These are explained below:

  • GET is a type of request that retrieves data from the server.
  • POST is a type of request used to submit fresh data form details and then upload a file.
  • PUT is a request similar to POST but applied for updating an existing entity.
  • DELETE is a request similar to PUT and is used to delete the resource from the server.
  • TRACE is used to validate content received along with the network during a request.
  • HEAD is similar to GET but receives response headers during the request.

Q #28) What are the differences between Span and Div tag in HTML5?

Answer: Div and Span are both used to represent a particular section of the webpage, but both differ from each other as explained in the table below:

Div is a block level elementSpan is an inline element
Div tag is used to wrap sections of documentSpan tag is used to wrap text and images in small portions
Div is used creating CSS based layoutsSpan is used to add style to text
Div accepts align attributeSpan does not accept align attribute

Q #29) Explain Pseudo class in CSS with examples.

Answer: Pseudo class in cascading style sheets is a keyword applied to HTML element’s selectors, to add special style on HTML events like onblur, onclick, onchange, onhover etc., in reference to external factors like previous website visit from navigation history, position or movement of the mouse, form element’s content status.

The syntax for Pseudo class:

cssselector : pseudo-class { attribute: value; }



CSS pseudo-class in HTML page:


Hovering mouse over different elements display effects of pseudo-class.


Thus, in this tutorial, we have discussed interview questions related to developing and maintaining websites and web-based applications. It is essential to have a good understanding and hands-on knowledge of integrating new technologies, front-end scripting language libraries, HTML5 APIs, CSS3, and languages like Java, ASP, PHP. Also, we must know to configure applications on web servers, and database, handling SEO keywords, web security, and browser compatibility.

You should be well versed with networking knowledge such as protocol, web services, user experience, problem-solving, and innovations in web and mobile applications as well as security, session handling, and accessibility features.

All the best with your upcoming Web Developer interview.