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40 Must-Know HTML Interview Questions & Answers in 2025

By Pavan Vadapalli

Updated on May 19, 2025 | 22 min read | 249.15K+ views

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Did you know that 98% of internet users in India access content in Indian languages? This make’s HTML’s semantic and accessibility features crucial for multilingual, mobile-friendly web experiences. Understanding HTML interview questions is essential for creating inclusive, global websites and improving user experience across diverse regions.

The top 40 HTML interview questions cover essential concepts like document structure, semantic markup, forms, multimedia integration, and performance optimization. These questions test your understanding of how browsers interpret and render web content, as well as your ability to write accessible and efficient code. 

Expertise of HTML fundamentals alongside modern practices like responsive design and SEO best practices is crucial for web development roles. This guide focuses on HTML, providing a comprehensive framework for preparing effectively in 2025.

Want to enhance your HTML skills for practical applications? upGrad’s Online Software Development Courses can equip you with tools and strategies to stay ahead. Enroll today!

40 Must-Know HTML Interview Questions & Answers 

HTML is the foundational markup language used to define and structure content on the web, enabling browsers to render text, multimedia, and interactive elements. It organizes web content through semantic tags like headings, paragraphs, anchors, and images, forming the Document Object Model (DOM) essential for dynamic manipulation. To help you prepare thoroughly, HTML interview questions are categorized into basic, intermediate, and advanced levels, covering everything from syntax to performance and accessibility best practices.

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Let’s look some of the basic HTML interview questions in details. 

Basic HTML Interview Questions 

These questions are designed to assess a candidate's foundational knowledge of HTML. They cover the basics of HTML structure, common tags, and how they’re used in web development. These are ideal for those just starting out or applying for entry-level roles in web development.

1. Explain the structure of an HTML document.

How to Answer:

Provide Overview:

An HTML document is the blueprint of web pages, defining the document’s structure for browsers to render. It starts with a declaration of the document type for compatibility (<!DOCTYPE html>) and is organized hierarchically into elements like <html>, <head>, and <body>. The <head> houses metadata, links to external resources like CSS or JavaScript files, and SEO tags, while <body> contains all user-visible content. This structure is fundamental for DOM manipulation in frameworks like ReactJS or server-side rendering in Node.js environments.

Discuss key elements:

  • <!DOCTYPE html>: Signals HTML5 compliance and standards mode to browsers, ensuring consistent rendering across clients.
  • <html>: The root element that encapsulates the entire HTML content and can specify language attributes (e.g., lang="en").
  • <head>: Contains metadata elements (<meta>), links to stylesheets (<link>), script files (<script>), and other resources necessary before page rendering.
  • <body>: Holds the DOM elements users interact with, including text, images, buttons, and dynamic ReactJS components.

Provide code example:

Code example 

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Sample HTML Document</title>
  <link rel="stylesheet" href="styles.css" />
  <script src="app.js" defer></script>
</head>
<body>
  <h1>Welcome to My Website</h1>
  <p>This is a basic HTML document structure.</p>
</body>
</html>

Output Explanation:

This code initializes a valid HTML5 document. Browsers parse the <head> first to load styles and scripts before rendering content inside <body>. Frameworks like ReactJS replace or manipulate this structure dynamically during runtime.

2. How do you create a hyperlink in HTML?

How to Answer:

Provide Overview:

Hyperlinks are core to web navigation, created using the anchor <a> tag with an href attribute specifying the target URL. Hyperlinks trigger HTTP requests to load resources or pages, facilitating SPA routing in frameworks like ReactJS or traditional multi-page sites served by Node.js backends. The target attribute controls the browsing context, with security attributes like rel="noopener noreferrer" mitigating vulnerabilities when opening new tabs.

Substantiate the core elements:

  • Use <a href="URL"> to define the link destination, where URL can be absolute (https://...) or relative (/page).
  • The link text between tags acts as the clickable anchor, important for accessibility and SEO.
  • Use target="_blank" cautiously to open links in new tabs, adding rel="noopener noreferrer" to prevent window object access exploits.

3. What are heading tags in HTML?

How to Answer:

Provide Overview:

Heading tags <h1> to <h6> establish a semantic hierarchy essential for search engine optimization and accessibility standards. Search engines prioritize content within these tags to understand page structure and improve content indexing. In ReactJS or server-side rendered applications, headings dynamically update to reflect route changes, maintaining semantic correctness. CSS styles can be applied to adjust visual importance without altering document semantics.

Discuss semantics:

  • <h1> is reserved for the primary page title or topic, ideally unique per page for clear SEO signals.
  • <h2> through <h6> create nested subsections, helping screen readers and crawlers parse content logically.
  • Proper use of headings enables automated table of contents and better keyboard navigation.

4. How do you create ordered and unordered lists in HTML?

How to Answer:

Provide Overview:

Lists organize content into sequences (<ol>) or groups (<ul>), enhancing readability and semantic clarity. Ordered lists are ideal for instructions or ranked items, while unordered lists suit categorical data. JavaScript frameworks like ReactJS dynamically generate list elements from arrays, leveraging keys to optimize rendering. CSS controls list styling, allowing custom markers and indentation to align with design systems.

Provide insights to items of HTML:

  • <ol> creates automatically numbered lists; list item order matters and can be manipulated with start and reversed attributes.
  • <ul> generates bulleted lists without inherent order; custom bullets can be styled with CSS pseudo-elements.
  • Each list item uses <li> tags containing nested lists, images, or complex HTML.

Provide code example:

Code Example:

<ol>
  <li>First item</li>
  <li>Second item</li>
</ol>

<ul>
  <li>Bullet one</li>
  <li>Bullet two</li>
</ul>

Output Explanation:

The ordered list displays numbered items; the unordered list shows bullet points. These structures improve UI clarity and SEO semantics.

5. How do you add an image to an HTML page?

How to Answer:

Provide Overview:

The <img> tag embeds images, with the src attribute specifying the file path or URL and alt providing descriptive text for screen readers and SEO. Responsive web design often pairs <img> with srcset and sizes attributes to deliver optimized images based on device characteristics. Modern web apps use lazy loading or JavaScript frameworks (ReactJS) to manage image rendering efficiently, improving page load times.

Discuss the process and practices:

  • Always include alt text to maintain accessibility standards and provide fallback descriptions if images fail to load.
  • Use relative paths for local assets and absolute URLs for external sources, considering CDN delivery for performance.
  • Utilize dimensions (width, height) or CSS to maintain aspect ratios and prevent layout shifts.

6. How do you create a paragraph in HTML?

How to Answer:

Provide Overview:

Paragraphs are block-level elements defined by <p>, grouping sentences or blocks of text semantically. Browsers apply default margin and line-height, which can be adjusted using CSS for readability and visual hierarchy. Frameworks like ReactJS render paragraphs as virtual DOM elements, enabling efficient updates during app state changes. Proper paragraph usage improves content structure and SEO.

Address key elements:

  • Each <p> starts on a new line and occupies full available width, enforcing logical content breaks.
  • Nesting block elements inside paragraphs is invalid and can cause rendering inconsistencies.
  • Use CSS for text alignment, font styling, and spacing instead of inline HTML tags.

7. What is the difference between inline and block-level elements?

How to Answer:

Provide Overview:

Block-level elements occupy the whole horizontal space, triggering line breaks and defining document flow, which is essential for page layout construction. Inline elements flow within text lines, affecting only their content width without disrupting the flow, enabling granular styling. Understanding this difference is crucial when manipulating the DOM with JavaScript or JSX in ReactJS, affecting event handling and layout rendering.

Discuss elements:

  • Common block elements: <div>, <p>, and <section> are often used as container elements for layout grids or components.
  • Common inline elements: <span>, <a>, <strong>, suitable for styling small portions of text or links.
  • CSS can change display properties (display: block; or display: inline;) to alter behavior without modifying HTML.

8. Why is the <alt> attribute important in the <img> tag?

How to Answer:

Provide Overview:

The alt attribute ensures web accessibility by providing descriptive text for images, read aloud by screen readers or displayed if images fail to load. It also enhances SEO by helping search engines understand image content, improving index relevance. Web frameworks like ReactJS encourage consistent use of alt to comply with WCAG standards and enhance user experience.

Provide understanding of the loaders and texts:

  • Omitting alt can lead to accessibility violations, negatively affecting users with visual impairments.
  • Descriptive alt text should succinctly convey the purpose or content of the image.
  • Dynamic content loaders should programmatically assign meaningful alt attributes.

If you want to learn the fundamentals of ReactJS, check out upGrad’s React.js For Beginners. The 14-hour free program will help you learn the components of React, along with analytical skills, and more. 

9. What are the <br> and <hr> tags used for?

How to Answer:

Provide Overview:

<br> creates line breaks within text without starting a new paragraph, useful for addresses, poems, or structured content formatting. <hr> inserts a thematic break as a horizontal line, visually dividing content sections. Both tags improve document readability and layout without complex CSS, which is commonly used in content-rich applications.

Discuss features:

  • <br> is an empty element; no closing tag is required.
  • <hr> can be styled with CSS for thickness, color, and margin adjustments to match design language.
  • Use <hr> semantically for section separation, not purely decorative purposes.

10. How do you link an external CSS file to an HTML document?
How to Answer:

Provide Overview:

External CSS enhances maintainability by separating styling from content, linked within the <head> using the <link> tag. This method uses HTTP caching and parallel resource loading for optimized page performance. In JavaScript frameworks like ReactJS, CSS files are often imported as modules, supporting scoped or dynamic styling approaches.

Explaining the characteriustics of links:

  • The rel="stylesheet" attribute specifies the relationship as a CSS stylesheet.
  • The href attribute points to the CSS file’s relative or absolute path.
  • Multiple CSS files can be linked for modular styles, allowing theme or component-based designs.

Also Read: Top 25+ HTML Project Ideas for Beginners in 2025

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Intermediate HTML Interview Questions

These questions focus on more advanced HTML concepts, such as HTML5 elements, forms, and how HTML interacts with CSS  and JavaScript. They help assess a deeper understanding of web development techniques.

These questions are suitable for developers with some hands-on experience in web development. If you’ve moved beyond the basics and have practical experience, this section is for you.

11. What is the difference between HTML and HTML5?

How to Answer:

Provide Overview:

In contrast to HTML, which offers basic structure and limited multimedia support, HTML5 introduces advanced features such as new semantic elements, native audio and video support, improved form controls, client-side storage, enhanced graphics capabilities, and better mobile optimization, making it more suitable for modern web development.

Discuss with a comparative analysis:

Take a look at this table highlighting the difference between HTML and HTML5:

Factor HTML HTML5
New Elements Limited structural elements like <div>, <span>. Introduced new semantic elements like <header>, <footer>, <article>, <section>, and <nav>.
Multimedia Support Relied on plugins like Flash for audio and video. Native support for audio (<audio>) and video (<video>) elements, eliminating the need for external plugins.
Graphics No native support for 2D graphics. Introduced <canvas> for drawing 2D graphics, enhancing interactive content.
Form Controls Basic form inputs, limited validation options. Introduced new input types (e.g., email, date, range) and built-in validation for better form handling.
Storage No native client-side storage. Introduced localStorage and sessionStorage for client-side data storage, enabling offline web apps.
Mobile Optimization No specific features for mobile devices. HTML5 is designed with mobile optimization in mind, supporting touch events and responsive design.

12. What is the difference between <article> and <section> in HTML5?

How to Answer:

Provide Overview:
Both <article> and <section> are semantic elements introduced in HTML5 to structure content meaningfully. Understanding their distinctions is critical for building accessible, SEO-friendly web pages and ensuring clear content organization, especially in modern frameworks like ReactJS and backend templating engines in Node.js.

Discuss key differences:

  • <article> encapsulates standalone content that can be independently distributed or reused, such as blog posts, news articles, or comments.
  • <section> groups thematically related content within a page, like chapters, tabs, or grouped UI components.
  • Using correct semantic tags aids assistive technologies in understanding document structure and improves search engine indexing.

13. How do you create a form in HTML? What are the different input types?
How to Answer:

Provide Overview:

HTML forms are critical for user input collection and act as interfaces between front-end and server-side logic in Node.js, Python, or C# applications. Various input types tailor the form to specific data, enabling browser validation and enhanced UX.

Explain the elements for the process:

  • Use <form> as the container element, with action URLs targeting backend endpoints.
  • Input types include text, password, email, number, date, and others, each optimized for specific data entry and mobile input methods.
  • <textarea> provides multi-line text input; <select> offers dropdown options.
  • Forms can be enhanced with JavaScript or ReactJS for dynamic validation and user feedback.

Provide code example:

Code Example:

<form action="/submit" method="POST">
  <label for="username">Username:</label>
  <input type="text" id="username" name="username" required />
  
  <label for="email">Email:</label>
  <input type="email" id="email" name="email" />
  
  <label for="password">Password:</label>
  <input type="password" id="password" name="password" required />
  
  <input type="submit" value="Register" />
</form>

Output Explanation:

This form collects username, email, and password inputs with client-side validation. On submission, data is sent via POST to the server endpoint /submit for backend processing in languages like Python or C++.

If you want to strengthen your programming skills, check out upGrad’s AI-Powered Full Stack Development Course by IIITB. The program will help you gather knowledge on frontend and backend development for enterprise applications. 

14. What is lazy loading and how do you implement it in HTML?
How to Answer:

Provide Overview:

Lazy loading optimizes web performance by deferring resource loading until needed, reducing initial page load times, a critical technique in bandwidth-constrained environments and SPA frameworks like ReactJS.

Discuss Key Points:

  • Add the attribute loading="lazy" to <img> and <iframe> tags to enable native browser lazy loading.
  • This defers fetching offscreen content until it approaches the viewport, improving performance and reducing HTTP requests.
  • Alternative JavaScript libraries or the Intersection Observer API can implement lazy loading for older browsers or advanced scenarios.

15. How do you create a table in HTML?
How to Answer:

Provide Overview:

HTML tables organize data in rows and columns, which is essential for presenting structured information. Tables integrate with backend data sources using Python or Node.js, dynamically generating rows and cells, while ReactJS can render tables efficiently using virtual DOM.

Discuss key points:

  • Structure tables with <table>, grouping headings in <thead>, data in <tbody>, and footers in <tfoot>.
  • Use <tr> for rows, <th> for header cells, and <td> for data cells.
  • Accessible tables should include scope attributes and captions for screen readers.

Provide code example:

Code Example:

<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Age</th>
      <th>Role</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Sashi Paul</td>
      <td>30</td>
      <td>Developer</td>
    </tr>
    <tr>
      <td>Raju Patel</td>
      <td>25</td>
      <td>Designer</td>
    </tr>
  </tbody>
</table>

Output Explanation:

This code generates a table with headers and two rows of data. Such tables can be dynamically generated from backend databases using Python or JavaScript in frameworks like Django or Node.js.

16. What is the purpose of the <meta> tag in HTML?
How to Answer:

Provide Overview:

The <meta> tag injects metadata into the document head, influencing character encoding, viewport behavior, and SEO metadata, key for responsive design and search engine optimization.

Address important factors:

  • <meta charset="UTF-8"> ensures correct character rendering across diverse languages.
  • <meta name="viewport" content="width=device-width, initial-scale=1"> enables mobile-friendly scaling.
  • Metadata like description and keywords guide search engines for indexing content accurately.

17. How do you ensure a website is accessible for screen readers?
How to Answer:

Provide Overview:

Accessibility involves semantic markup, ARIA roles, and meaningful attributes, which are critical for inclusive design and compliance with standards like WCAG. Frameworks such as ReactJS support accessibility through built-in properties and components.

Address features:

  • Use semantic HTML5 tags (<nav>, <main>, <header>) to structure content logically.
  • Provide descriptive alt text for images and aria-labels for interactive elements.
  • Test with screen readers and accessibility audit tools integrated in modern IDEs or browsers.

18. What’s the difference between <div> and <span> elements?
How to Answer:

Short overview:

<div> and <span> are fundamental HTML elements serving different layout purposes: block-level vs inline, impacting styling and document flow.

Discuss differences:

  • <div> is block-level, creating vertical space and stacking content; it’s widely used as a container for layout and components.
  • <span> is inline, affecting only its content width and useful for styling parts of text without disrupting flow.
  • Both are extensively manipulated in JavaScript frameworks like ReactJS for dynamic rendering.

19. What is the purpose of the <nav> tag in HTML5?
How to Answer:

Short Overview:

The <nav> element semantically defines navigation regions, improving SEO and assistive technology support by grouping site navigation links distinctly.

Address core purposes:

  • Encloses primary navigation menus, site maps, or table of contents.
  • Improves document outline and facilitates keyboard navigation in SPA architectures.
  • Can be styled and manipulated dynamically using JavaScript or ReactJS components.

20. Why are semantic tags like <header>, <footer>, and <article> important?
How to Answer:

Provide Overview:

Semantic tags clarify the role of different page sections, enabling better SEO and accessibility. They form the backbone of structured web content used by modern frameworks and search engines.

Address the importance of semantics:

  • <header> marks introductory content or navigation at the top of pages or sections.
  • <footer> contains closing or supplemental information at the page or section end.
  • <article> denotes standalone content like blog posts or news items.
  • Proper usage improves readability, SEO ranking, and assistive device navigation.

21. How do you embed a video or audio file in an HTML page?
How to Answer:

Provide Overview:

Embedding multimedia in HTML uses <video> and <audio> tags with multiple source support for compatibility. JavaScript frameworks enhance these elements with custom controls, while backend systems handle streaming and adaptive bitrate delivery.

Explain the process:

  • Use <source> tags inside media elements to specify multiple formats (MP4, WebM, Ogg).
  • Add controls attribute to display native playback UI.
  • Integrate with JavaScript APIs for programmatic control, event handling, and analytics.

Provide codes:

Code Example:

<video width="640" controls>
  <source src="movie.mp4" type="video/mp4" />
  <source src="movie.webm" type="video/webm" />
  Your browser does not support the video tag.
</video>

Output Explanation:

Renders a video player with playback controls. The browser chooses the supported format and falls back to a message if unsupported.

22. How do you ensure cross-browser compatibility with HTML code?
How to Answer:

Provide Overview:

Cross-browser compatibility requires adherence to web standards, CSS resets like Normalize.css, and progressive enhancement. Testing across environments with tools such as BrowserStack or Selenium automates quality assurance for diverse browsers and devices.

Comprehensive explanation:

  • Use feature detection and polyfills to handle unsupported HTML or CSS features.
  • Follow semantic HTML and W3C specifications for best compatibility.
  • Employ testing frameworks to validate behavior in browsers like Chrome, Firefox, Edge, and Safari.

23. What are ARIA roles, and how do they improve accessibility in HTML?

How to Answer:

Provide Overview:

ARIA (Accessible Rich Internet Applications) roles are special attributes that can be added to HTML elements to enhance web accessibility for people with disabilities, especially those using screen readers or other assistive technologies. 

Discuss the role of ARIA:

ARIA roles help define elements for screen readers. Add role, aria-label, and aria-described by attributes to make the page accessible. "Use role='navigation', aria-label for better descriptions, and aria-described to improve accessibility for users relying on screen readers."

Discuss the accessibility feature of ARIA:

Here's how ARIA roles improve accessibility:

  • Semantic clarity: ARIA roles give meaning to elements, ensuring that assistive technology can describe their function to the user.
  • Enhanced navigation: ARIA roles provide a way to make custom widgets (e.g., sliders, accordions, etc.) accessible.
  • Improved interaction: Elements like buttons, links, and navigation items can be identified with specific ARIA roles, enabling users to navigate more easily.

24. How do you implement responsive web design in HTML?

How to Answer:

Provide Overview:

Responsive Web Design (RWD) ensures that a web page adapts to different screen sizes and device types (like desktops, tablets, and smartphones). It typically involves a combination of flexible layouts, media queries, and responsive images.

Discuss how to implement responsive design:

These are the ways to implement responsive design:

  1. Viewport meta tag: This tag ensures the page is scaled correctly on various devices.
  2. CSS Media Queries: Media queries enable different styles for different screen sizes.
  3. Fluid Layouts: Use percentage-based widths instead of fixed pixel widths so elements can resize fluidly.
  4. Responsive Images: Use the srcset attribute for images to serve different image sizes based on screen resolution.
  5. Flexible Grid System: Many frameworks like Bootstrap provide a flexible grid system that adjusts the layout based on screen size.

25.  How can you create a multi-page, nested website structure using HTML?

How to Answer:

Provide Overview:

To create a multi-page, nested website structure, you organize your content into several HTML files and use navigation links to connect them. A nested structure typically means having different sections or categories inside your website that users can explore.

Explain in a stepwise manner:

Here's how you can set it up:

Step 1 - Create Multiple HTML Pages: For each page, you create a separate .html file (e.g., index.html, about.html, contact.html, etc.).

Step 2: Directory Structure: Organize your files into folders. For example:

/ (root directory)
├── index.html
├── about.html
├── contact.html
└── /assets
    ├── style.css
    └── images

Step 3 - Links Between Pages: You can use <a> tags to link the different pages together in the navigation menu.

<nav>
  <ul>
    <li><a href="index.html">Home</a></li>
    <li><a href="about.html">About</a></li>
    <li><a href="contact.html">Contact</a></li>
  </ul>
</nav>

Step 4- Nested Content: Inside each HTML file, you can nest elements inside <div>, <section>, <article>, etc., to organize the content in a structured manner.

<div class="main-content">
  <section>
    <h1>About Us</h1>
    <p>Information about the company.</p>
  </section>
</div>

Step 5 - Styling and Layout: Use CSS to style the navigation menu, headers, and content areas. Ensure that the layout works well across the different pages.

Now, let’s explore some of the advanced HTML interview questions for modern enterprises.

Advanced HTML Interview Questions 

In this section on advanced-level HTML interview questions, we shall delve into more complex topics in HTML, such as performance optimization, advanced HTML5 features, and SEO integration. The focus is on writing efficient, clean, and scalable code.

These questions are designed for senior developers or advanced web designers who are experienced in web development and want to demonstrate expertise in advanced HTML concepts and best practices.

26. How do you optimize images in HTML for faster load times?
How to Answer:

Provide Overview:

Optimizing images reduces load time and bandwidth consumption, making websites more efficient, especially for mobile users and those on slow networks. Techniques like responsive image handling with srcset, compression formats like WebP, and lazy loading can significantly improve performance. Modern HTML5 websites, particularly those deployed on cloud platforms like AWS or Azure, benefit from these optimizations for both user experience and SEO.

Discuss key elements:

  • Use the srcset and sizes attributes to serve different image sizes based on the viewport and device resolution.
  • Compress images using modern formats like WebP or AVIF to reduce file size without compromising quality.
  • Implement lazy loading (loading="lazy") to defer the loading of offscreen images, improving initial load time.
  • Use CDNs (e.g., AWS CloudFront) to serve images efficiently across regions, reducing latency.

Provide code examples:

Code Example:

<img src="image.webp" 
    alt="Optimized image" 
    width="600" height="400"
    srcset="image-400.webp 400w, image-800.webp 800w" 
    sizes="(max-width: 600px) 400px, 800px" />

Output Explanation:

The browser will choose the best image source based on the viewport size. This reduces unnecessary bandwidth usage and ensures that the appropriate image size is loaded, improving page load times.

27. Explain the purpose of the <canvas> and <audio> elements in HTML5.
How to Answer:

Provide Overview:

The <canvas> element allows for dynamic, scriptable rendering of 2D graphics, enabling developers to create complex visual content, animations, and games, often used with JavaScript libraries or frameworks like TensorFlow.js for machine learning applications. The <audio> element, on the other hand, embeds audio content with playback controls, widely used for multimedia-rich applications and data-driven sound analysis.

Discuss the features of canvas and audio:

  • <canvas> is used for drawing and rendering graphics like charts, games, or custom animations using JavaScript.
  • <audio> embeds sound content, and is designed for easy playback without additional plugins, supporting multiple audio formats.
  • Both elements are commonly used in interactive web applications, such as games, dashboards, or media players.

Provide code examples:

Code Example:

<canvas id="myCanvas" width="200" height="100"></canvas>
<script>
  const canvas = document.getElementById('myCanvas');
  const ctx = canvas.getContext('2d');
  ctx.fillStyle = 'blue';
  ctx.fillRect(10, 10, 150, 80);
</script>

<audio controls>
  <source src="audio.mp3" type="audio/mpeg" />
  Your browser does not support the audio element.
</audio>

Output Explanation:
The <canvas> renders a blue rectangle dynamically with JavaScript, while the <audio> element provides a player to control audio playback. This is essential for rich media applications in ReactJS or similar JavaScript-based frameworks.

28. How does the <title> tag impact SEO? What HTML tags are crucial for SEO optimization?
How to Answer:

Provide Overview:

The <title> tag plays a pivotal role in SEO as it defines the title displayed in search engine results and browser tabs, which directly affects click-through rates. In addition to the title, other HTML tags like <meta>, <h1>, and <alt> help search engines index content effectively. SEO optimization practices are essential when creating web pages that need to rank well in search engines, especially when dealing with dynamic content rendered in ReactJS.

Comprehensive explanation:

  • The <title> tag defines the title of the web page, which appears in search engine results and browser tabs.
  • Meta tags (<meta name="description">, <meta name="keywords">) provide additional information that search engines use to index the page.
  • <h1> tags define the main heading of the page, improving SEO by indicating content hierarchy
  • The alt attribute for images improves image searchability and accessibility

Provide code examples:

Code Example:

<head>
  <title>Best Practices for HTML and SEO Optimization</title>
  <meta name="description" content="Learn HTML best practices for optimizing your web pages for SEO and improving search engine ranking." />
</head>
<body>
  <h1>SEO and HTML Best Practices</h1>
  <img src="seo-image.jpg" alt="SEO Optimization" />
</body>

Output Explanation:
The <title> tag improves SEO by providing a concise description of the page, while the <meta> tag and alt text enhance the visibility of the page for search engines, especially important for dynamic content rendered in ReactJS.

29. What are some best practices for writing clean HTML code?
How to Answer:

Provide Overview:

Clean HTML is the foundation of efficient web development. Following best practices ensures that the code is maintainable, accessible, and semantically correct. In frameworks like ReactJS or server-side rendered apps in Node.js, maintaining clean HTML improves both development speed and user experience by making the codebase more modular and readable.

Address key elements:

  • Use semantic HTML tags (<header>, <footer>, <section>) to convey meaning and improve accessibility.
  • Maintain proper indentation (2-4 spaces) for clarity and readability.
  • Avoid inline styles; link to external CSS for modular design and better maintainability.
  • Comment sections of code to describe functionality, especially in complex applications.
  • Ensure that the HTML is valid and passes W3C validation.

Provide codes:

Code Example:

<header>
  <h1>Web
    <ul>
      <li><a href="/">Homsite Header</h1>
  <nav>e</a></li>
      <li><a href="/about">About</a></li>
    </ul>
  </nav>
</header>
<section>
  <h2>Main Content</h2>
  <p>Here's some content...</p>
</section>

Output Explanation:

Using semantic elements (<header>, <nav>, <section>) enhances the structure and readability of the document. This also improves SEO by clarifying the purpose of different sections within the page.

30. How would you improve a web page’s load time using HTML optimizations?
How to Answer:

Provide Overview:

Optimizing load time is critical for improving user experience and SEO. HTML optimizations, such as image compression, lazy loading, and script deferring, significantly reduce the time it takes for a page to load and become interactive. Using techniques like minifying HTML and CSS files, implementing asynchronous loading, and leveraging CDNs further enhances performance, particularly for modern web apps built with ReactJS or server-side frameworks like Node.js.

Discuss Key Points:

  • Compress images to reduce file size without compromising quality, and implement srcset for responsive image loading.
  • Use lazy loading for images and iframes to defer loading of non-essential content.
  • Minify HTML, CSS, and JavaScript files to reduce file size.
  • Defer or asynchronously load JavaScript files to prevent render-blocking.
  • Implement CDN services like AWS CloudFront for faster content delivery.

Provide codes:

Code Example:

<img src="image.jpg" alt="Optimized Image" loading="lazy" width="600" height="400" />
<script src="script.js" defer></script>

Output Explanation:

The image is only loaded when it’s in the viewport, while the script is deferred until after the HTML parsing is complete, improving overall load time.

31. How do you optimize <script> loading to improve page performance?
How to Answer:

Provide Overview:

Optimizing <script> loading involves using attributes like async and defer to prevent blocking of page rendering. In ReactJS and other JavaScript-heavy applications, deferring scripts allows the HTML and CSS to load first, improving the time-to-interactive for users. By using techniques like code splitting or lazy loading, you can load only the necessary scripts as required, reducing initial page load time.

Address features:

  • Use async for independent script loading that doesn’t depend on other resources or DOM elements.
  • Use defer for scripts that should execute after the document is parsed, ensuring non-blocking page load.
  • Split JavaScript into smaller bundles to load code on demand, especially in single-page applications (SPA) built with ReactJS or other JS frameworks.

Provide codes:

Code Example:

<script src="critical.js" async></script>
<script src="main.js" defer></script>

Output Explanation:

The async attribute allows the critical.js script to load independently, while main.js will execute after the HTML is parsed, improving load times without blocking page rendering.

32. How can you use data- attributes to store custom data in HTML elements?
How to Answer:

Provide Overview:

data-* attributes allow developers to store custom data directly within HTML elements, which can later be accessed and manipulated using JavaScript. This is ideal for passing small pieces of data, such as IDs or configuration settings, in dynamic web applications or when interacting with APIs in backend technologies like Python or Node.js.

Address core elements:

  • Use data-* attributes to store arbitrary data, accessible via JavaScript’s dataset property.
  • This method allows the storage of non-visible information that doesn't interfere with element styling or behavior.
    Ideal for use in modern JavaScript frameworks like ReactJS or when integrating dynamic functionality with backend APIs.

Provide code examples:

Code Example:

<div data-user-id="12345" data-role="admin">User Info</div>

<script>
  const userDiv = document.querySelector('div');
  console.log(userDiv.dataset.userId);  // Outputs: 12345
  console.log(userDiv.dataset.role);    // Outputs: admin
</script>

Output Explanation:

The data-user-id and data-role attributes store custom data that can be accessed and manipulated by JavaScript, enabling dynamic UI changes or backend communication.

33. What is the function of the meter element in HTML5?

How to Answer:

Explain meter element:

The <meter> element in HTML5 is used to represent a scalar measurement within a known range, such as a progress bar or a rating system. It is typically used to display a value that is part of a predefined range, like disk usage, a score, or a temperature.

Explain with a code example:

In the following example, the <meter> element shows the battery level as 60% of its total capacity, with the range defined from 0 to 1: 

<label for="battery">Battery Level:</label>
<meter id="battery" value="0.6" min="0" max="1"></meter>

34. What is the Shadow DOM in HTML?

The Shadow DOM is a web standard that allows for the encapsulation of HTML, CSS, and JavaScript within a web component. It enables developers to create self-contained, reusable components with isolated styles and behaviors that do not interfere with the global document. The Shadow DOM is a key part of Web Components and allows components to maintain their own internal DOM structure while remaining separate from the main document's DOM.

Discuss components of DOM:

The key components of Shadow DOM are:

  • Encapsulation: Isolates component’s DOM, styles, and behavior from the main document.
  • Isolation: Styles inside the Shadow DOM don't affect the global document.
  • Shadow Tree: A separate DOM structure within the shadow root, isolated from the main DOM

This is how it works:

  • First, you create a shadow root attached to a host element, and then you can add content to the shadow tree using JavaScript.
  • The shadow root can be either in open or closed mode.

Explain the process of creating a Shadow DOM in HTML:

Here’s how you can create a Shadow DOM in HTML:

<!-- Host Element -->
<div id="host"></div>


<script>
  // Attach Shadow DOM to host element
  const shadowRoot = document.getElementById('host').attachShadow({mode: 'open'});


  // Add content to the shadow DOM
  shadowRoot.innerHTML = `
    <style>
      p { color: red; }
    </style>
    <p>This is inside the Shadow DOM</p>
  `;
</script>

35. How can you convert an inline element into a block-level element?

How to Answer:

Provide Overview:

Discuss the process:

To convert an inline element into a block-level element, CSS is used to modify the display property of the element. By changing the display type, the behavior of the element can be adjusted to occupy the full width of its parent container.

Here’s how you can convert an inline element into a block-level element:

  • Use the display: block; CSS property to convert inline to block.
  • Inline elements like <span> will behave like block-level elements, e.g., <div>.
  • The element will now take up the entire width and start on a new line.

36. What is the difference between the <progress> and <meter> tags in HTML?

How to Answer:

Discuss the differences:

The <progress> and <meter> tags in HTML5 are both used to represent measurements, but they serve different purposes. The <progress> tag is used to represent the completion of a task, often with a value indicating the percentage of progress. It is typically used for tasks like file uploads or loading processes, where a value between 0 and 1 (or 0 to 100) reflects the progress. 

On the other hand, the <meter> tag is used to represent a value within a known range, like a scale or gauge. It’s commonly used for things like disk usage or a rating system, where the value is within a specific range (e.g., 0 to 100), but it doesn't reflect the completion of a task. Essentially, while both tags represent measurements, <progress> is for task progress, and <meter> is for scalar data within a range.

37. How do WebSockets in HTML5 enable real-time communication in web applications,?

How to Answer:

Provide explanation briefly:

WebSockets in HTML5 provide a mechanism for establishing a persistent, full-duplex communication channel between a web browser (client) and a server. Unlike traditional HTTP requests, which are one-way and stateless, WebSockets allow both the client and the server to send and receive data at any time over a single connection.

WebSockets in HTML5 enable real-time, interactive communication by maintaining an open connection that allows messages to be sent back and forth between the client and server with minimal delay. This is especially useful for applications that require live updates and instant data exchange.

Discuss its working principles:

Here's how they work: 

  1. Connection Establishment: The WebSocket protocol starts with a handshake initiated by the client, upgrading the HTTP connection to a WebSocket connection.
  2. Full-Duplex Communication: Once the connection is established, data can flow in both directions (from client to server and vice versa) without the need to repeatedly open new connections.
  3. Persistent Connection: The connection remains open until either the client or the server decides to close it, enabling continuous, real-time data transfer.

Explain with a code example:

Below is an example of the use of WebSocket:

// Open WebSocket connection
const socket = new WebSocket('ws://example.com/socket');


// When the connection is open
socket.onopen = function(event) {
    console.log('Connection established');
    socket.send('Hello Server!');
};


// When a message is received from the server
socket.onmessage = function(event) {
    console.log('Message from server: ', event.data);
};


// When the connection is closed
socket.onclose = function(event) {
    console.log('Connection closed');
};

38. What is MathML in HTML5, and how is it used to display mathematical content?

How to Answer:

Directly address with MathML:

MathML (Mathematical Markup Language) is an XML-based language used to represent mathematical notations and structures within web pages. In HTML5, MathML enables the inclusion of complex mathematical formulas, equations, and symbols directly in the HTML document. It allows for a semantically rich and accessible representation of mathematical content, which can be styled and manipulated using CSS and JavaScript.

Address the features of MathML:

Here is how MathML is used to display mathematical content:

  • Mathematical expressions: MathML tags like <math>, <msup>, <mfrac>, and <mi> represent mathematical symbols, fractions, and operators.
  • Accessibility: MathML allows screen readers to interpret and read out mathematical content for visually impaired users.
  • Direct embedding: You can embed equations directly in HTML5 documents without the need for external images or plugins.
  • Presentation and structure: MathML provides a structured way to display equations (e.g., inline or block-level) with proper formatting, ensuring clarity.
  • Cross-browser support: While support is growing, MathML content may render differently in some browsers, so fallback options like images or alternative markup may be required for full compatibility.

39. What techniques can you use to make HTML forms accessible for users with disabilities?

How to Answer:

Brief overview:

Ensuring accessibility in HTML forms is crucial for providing an inclusive web experience for users with disabilities. Below are several techniques to enhance the accessibility of HTML forms:

Discuss core elements:

1. Use Semantic HTML

  • Labels: Always associate form fields with <label> elements for screen readers
  • Fieldset & Legend: Group related fields for clarity

2. ARIA Attributes

  • aria-required: Indicate required fields
  • aria-invalid: Notify screen readers of invalid inputs.

3. Keyboard Accessibility

  • Ensure form fields are navigable via the Tab key.
  • Buttons should be focusable and triggerable via the keyboard.

4. Error Handling and Feedback

  • Use ARIA live regions for error messages.

5. Provide Clear Instructions

  • Use descriptive placeholder text and button labels, but never replace labels with placeholders.

6. Visual Clarity and Focus

  • Ensure sufficient color contrast (at least 4.5:1) and clear focus indicators for keyboard navigation.

40. How does the <canvas> element in HTML5 work, and how does it compare to the <svg> element in terms of rendering methods and ideal use cases?

How to Answer:

Provide Overview:

The <canvas> element in HTML5 is used to draw graphics dynamically via JavaScript. It provides a drawable area in the form of a bitmap, where pixels can be manipulated directly. The <canvas> element is primarily used for rendering graphics, animations, and interactive visualizations. Here's a detailed breakdown of how it works and how it compares to the <svg> element.

Explain the working principle of Canvas:

How the <canvas> Element Works:

1. Basic Structure:

  • The <canvas> element itself doesn’t contain any visual content. Instead, it provides a drawing surface, and its content is rendered through JavaScript.
  • The canvas is defined by its width and height attributes.

Discuss rendering through JavaScript:

2. Rendering via JavaScript:

  • JavaScript is used to draw graphics on the canvas. A “CanvasRenderingContext2D”  object is used to interact with the canvas and draw shapes, images, and other objects.

Discuss with a code example:

This is an example of a drawing on canvas:

var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
ctx.fillStyle = 'red';
ctx.fillRect(10, 10, 100, 100); // Draw a red rectangle

Discuss Pixel-based rendering:

3. Pixel-Based Rendering:

  • The <canvas> uses pixel-based rendering (bitmap). The content is drawn as pixels, so it’s resolution-dependent.
  • It is ideal for situations where you need to draw low-level pixel manipulation (such as games, simulations, and complex drawings).

Explain with a comparative analysis:

Following is a comparison between <canvas> and <svg> elements:  

Factor

<canvas>

<svg>
Rendering Model Bitmap-based (pixel manipulation) Vector-based (geometric shapes, paths)
Use Case Ideal for complex, dynamic graphics like games, animations, and image manipulation. Ideal for scalable, static, or simple interactive graphics like icons, logos, and charts.
Performance Better for real-time rendering with lots of dynamic content (e.g., games, complex animations). Can be less efficient with many elements, but works well for simple or static graphics.
Scalability Resolution-dependent (loses quality when zoomed or resized). Scalable without losing quality (resizes cleanly at any resolution).
Manipulability Once drawn, content cannot be easily manipulated; you need to redraw it. Each individual element (circle, rectangle, path, etc.) is part of the DOM and can be easily manipulated via JavaScript and CSS.
Interactivity Less suitable for individual element interactivity; works well for fast, frame-based updates. Very suitable for interactivity, as each element can be targeted and manipulated individually (e.g., clickable elements, CSS animations).

Let’s understand some of the tips you can use while preparing for HTML interview questions.

Useful Tips for HTML Interview Preparation 

Preparing for an HTML interview requires a combination of technical knowledge and practical problem-solving skills. Here are some tips to help you get ready:

  • Review the Basics: Make sure you're confident with fundamental HTML concepts, such as document structure, tags, and attributes, and common elements like links, lists, and images.
  • Practice Coding: Regularly write and troubleshoot HTML code. You may be asked to write or debug HTML during the interview so that hands-on practice will boost your confidence.
  • Understand HTML5 Updates: Be familiar with the latest HTML5 features, such as semantic elements (<article>, <section>, <nav>), multimedia elements (<video>, <audio>), and new input types.
  • Brush Up on SEO and Accessibility: Interviewers often test your knowledge of SEO-friendly HTML practices (like using <title>, <meta>, and <alt> tags) and accessibility standards (like ARIA roles and attributes).
  • Focus on Real-World Application: Be prepared to discuss how you’ve used HTML in previous projects, particularly how you’ve optimized websites for performance, user experience, or search engine rankings.
  • Work on Mock Tests: Try practicing with mock HTML interview questions or take coding tests to simulate the actual interview environment and time constraints.

Also read: Top 25+ HTML Project Ideas for Beginners in 2025: Source Code, Career Insights, and More

Career in HTML and Web Development 

  • A career in HTML and web development offers you the opportunity to build and maintain websites, ensuring they are both functional and visually appealing. With a solid understanding of HTML, CSS, and JavaScript, you can take on various roles in web development, ranging from front-end to full-stack positions. 

    Below, you'll find detailed information on key roles in the industry, along with their typical salaries, to help guide your career path.

Role

Average Annual Salary 

Responsibilities

Front-End Developer

INR 6L

- Build and optimize website interfaces

- Ensure responsive design

- Work with designers and back-end developers

Web Designer

INR 3L

- Create visually appealing layouts

- Focus on the aesthetics and branding

- Ensure user-friendly designs

UI/UX Developer

INR 5L 

- Design user interfaces and experiences

- Conduct user research

- Create wireframes and prototypes

Email Developer

INR 6L

- Design and code email templates

- Optimize for different email clients

- Manage email marketing campaigns

Full-Stack Developer

INR 7L

- Develop both front-end and back-end components

- Ensure seamless integration between the two

- Maintain full-stack architecture

Web Development Manager

INR 3L

- Lead and manage a web development team

- Oversee project timelines and budgets

- Coordinate between developers and other departments

Source: Glassdoor

Also read: 30+ Best HTML Project Ideas and Topics for Beginners and Professionals in 2025

Conclusion 

The top HTML interview questions cover document structure, semantic tags, forms, multimedia embedding, performance optimization, and accessibility standards essential for modern web development. Focus on writing clean, accessible, and SEO-friendly code while applying techniques like lazy loading and asynchronous script loading to improve performance. Practice building projects with ReactJS and backend frameworks like Node.js to strengthen your skills and excel in technical interviews.

If you want to learn HTML that can secure you a career in tech sectors. These are some of the additional courses that can help understand HTML at its core. 

Curious which courses can help your learn HTML? Contact upGrad for personalized counseling and valuable insights. For more details, you can also visit your nearest upGrad offline center. 

Boost your career with our popular Software Engineering courses, offering hands-on training and expert guidance to turn you into a skilled software developer.

Master in-demand Software Development skills like coding, system design, DevOps, and agile methodologies to excel in today’s competitive tech industry.

Stay informed with our widely-read Software Development articles, covering everything from coding techniques to the latest advancements in software engineering.

References:
https://www.hindustantimes.com/india-news/study-predicts-indias-internet-users-will-cross-900-mn-by-2025-with-increased-adoption-of-indic-languages-101737026654421.html
https://www.glassdoor.co.in/Salaries/front-end-developer-salary-SRCH_KO0,19.htm
https://www.glassdoor.co.in/Salaries/web-designer-salary-SRCH_KO0,12.htm
https://www.glassdoor.co.in/Salaries/ui-ux-developer-salary-SRCH_KO0,15.htm
https://www.glassdoor.co.in/Salaries/email-developer-salary-SRCH_KO0,15.htm
https://www.glassdoor.co.in/Salaries/full-stack-developer-salary-SRCH_KO0,20.htm
https://www.glassdoor.co.in/Salaries/website-manager-salary-SRCH_KO0,15.htm

Frequently Asked Questions (FAQs)

1. What are semantic HTML tags, and why are they important?

2. How does HTML handle responsive web design?

3. What role do forms play in HTML, and how do you ensure data integrity?

4. How can I optimize HTML for better SEO performance?

5. What is the difference between inline and block-level elements in HTML?

6. How can HTML be integrated with JavaScript for dynamic content?

7. How does HTML support multimedia content, such as videos and audio?

8. What is the <meta> tag used for in HTML?

9. How do you ensure a website is accessible for screen readers?

10. What’s the difference between <div> and <span> elements?

11. What is the purpose of the <nav> tag in HTML5?

Pavan Vadapalli

900 articles published

Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology s...

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