What is HTML?

Reviewed by: Christine Hoang

15 November 2024

Inside this Article

Definition of HTML How Does HTML Work?HTML Elements and Tags HTML Documents HTML Versions and Standards Semantic HTML HTML and SEO HTML Best Practices HTML and Web Development HTML and the Future of the Web

HTML (HyperText Markup Language) is the standard markup language used to create web pages. It defines the structure and content of webpages using a series of elements represented by tags.

Developers use HTML to build the framework of a website, organizing content like text, images, videos and interactive forms. Web browsers then read this HTML code to render and display the page’s content for users to view and interact with.

Definition of HTML

HTML is a markup language that instructs web browsers how to structure and present content on a webpage. Rather than using programming to perform functions, HTML uses tags to identify different types of content and the purposes they each serve on the webpage.

An HTML element contains an opening tag, content, and a closing tag. Some key examples include:

<head> – Contains metadata about the page, such as the title
<title> – Specifies the title of the webpage
<body>- Defines the main content of the webpage
<h1> to <h6> – Represents different levels of section headings
<p> – Marks a paragraph of text
<img> – Embeds an image into the page
<a> – Creates a hyperlink to another webpage or resource

This hierarchical structure of nested elements forms the backbone of any website. HTML allows web developers to logically organize content and present it in a way that’s meaningful for users.

How Does HTML Work?

HTML works together with CSS (Cascading Style Sheets) and JavaScript to form the front-end of a website or web application. Here’s a simple analogy to understand their roles:

If a webpage were a person, the HTML would represent their skeleton, providing the basic structure.
CSS would represent their clothing, hairstyle, and makeup, enhancing the presentation.
JavaScript would represent their actions, like walking or talking, adding interactivity.

When you type a URL into your browser or click a link, the browser sends a request to a web server. The server then responds with an HTML document. The browser reads this HTML code, processes it, and creates the Document Object Model (DOM). The DOM represents the page structure and content, which the browser uses to render the webpage you see.

HTML tags are not visible to users, but their effects are. Browsers use tags to determine how to format and display the content. The <img> tag, for example, instructs the browser to request and display an image, while the <a> tag creates a hyperlink to another web page or resource.

While HTML is primarily concerned with structure and semantics, modern HTML also includes ways to embed styling (CSS) and scripts (JavaScript) alongside the structural layer. This allows for more dynamic, interactive websites.

HTML Elements and Tags

HTML documents are composed of a tree of HTML elements and other nodes, like text nodes. Each element is denoted in the source by a start tag, such as <body>, and an end tag, such as </body>. Some start tags don’t require an end tag or have an empty end tag, like <img>.

The opening tag can also contain additional information using attributes. Attributes are key-value pairs that provide more details about the element. For example:

Here, src and alt are attributes of the <img> tag. The src attribute specifies the URL of the image to display, while alt provides alternative text for the image if it can’t be displayed or for screen readers.

There are many HTML tags, each serving a specific purpose. Some common ones include:

<html>: Represents the root (top-level element) of an HTML document.
<head>: Contains metadata about the HTML page, like its title, scripts, and style sheets.
<title>: Defines the title of the document, shown in a browser’s title bar or page’s tab.
<body>: Represents the content of an HTML document. There can be only one <body> element in a document.
Headings: <h1> to <h6> represent six levels of section headings, with <h1> being the highest and <h6> the lowest.
<p>: Defines a paragraph.
<div>: Defines a general container for flow content, usually used for grouping and styling.
<span>: Defines an inline container used for grouping and styling.
<img>: Embeds an image into the document.
<a>: Creates a hyperlink to other web pages, files, locations within the same page, email addresses, or any other URLs.

These are just a few of the over 100 available HTML tags. Each plays a specific role in structuring the webpage’s content.

HTML Documents

Every HTML document starts with a document type declaration: <!DOCTYPE html>. This tells the browser that this is an HTML5 document. After this, the actual HTML code follows, starting with <html> and ending with </html>.

Inside the HTML document, there are two main sections: the head (<head>) and the body (<body>). The head contains metadata about the page that isn’t directly visible to users, like the page title (<title>), stylesheets (<link>), scripts (<script>), and more. The body contains all the content that users see and interact with when they load a webpage.

Here’s a basic structure of an HTML document:

<!DOCTYPE html>
<html lang=”en”>
<head>
<meta charset=”UTF-8″>
<title>Page Title</title>
</head>
<body>
<h1>My First Heading</h1>
<p>My first paragraph.</p>
</body>
</html>

This simple HTML document has:

The <!DOCTYPE html> declaration defining the document type.
The <html> element, which is the root element of the HTML page.
The <head> element, containing metadata about the page.
- A <meta> element specifying the document’s character encoding.
- A <title> element specifying the page’s title.
The <body> element, containing the visible page content.
- An <h1> element for the main heading.
- A <p> element for a paragraph of text.

When a browser reads this code, it will render a webpage with “Page Title” in the title bar (or tab), a heading displaying “My First Heading”, and a paragraph of text reading “My first paragraph.”

HTML Versions and Standards

HTML has evolved significantly since its creation. The first official version, HTML 2.0, was published in 1995. HTML 4.01, published in 1999, was a major version that was widely used for over a decade.

However, the most significant change to HTML came with HTML5, which was first published in 2014. HTML5 introduced many new semantic elements like <header>, <footer>, <article>, and <section>, which describe the purpose of the content they contain. This made HTML more understandable for developers, users, and search engines.

HTML5 also introduced new APIs that allow complex web applications to be built. These include APIs for playing audio and video, drag-and-drop, browser storage, and more.

Currently, HTML is a living standard. This means that it’s constantly evolving, with new features and changes being added as needed. However, this doesn’t mean that there will be an HTML6. Instead, the version number is no longer relevant. The standard simply evolves, with browsers adopting new features as they’re defined and agreed upon by the standards committees like the W3C (World Wide Web Consortium) and the WHATWG (Web Hypertext Application Technology Working Group).

Developers should always aim to use the latest features supported by the browsers their users are likely to employ. They can check the compatibility of different HTML features across browsers using resources like caniuse.com.

Semantic HTML

HTML has always been about marking up content with meaning. However, in the early days of the web, developers often used HTML elements in ways they weren’t intended, like using <table> elements for layout instead of displaying tabular data.

Semantic HTML is a modern approach where the focus is on using HTML elements for their intended purpose based on their semantic meaning. For example, instead of using a <div> element with a class of “header”, you would use the semantic <header> element.

Here are some semantic elements introduced in HTML5:

<article>: Defines an independent piece of content that could theoretically be distributed separately from the rest of the site, like a news article or blog post.
<aside>: Defines a portion of a document whose content is only indirectly related to the main content, like a sidebar.
<figcaption>: Defines a caption for a <figure> element.
<figure>: Represents self-contained content, like illustrations, diagrams, photos, or code listings.
<footer>: Represents a footer for a document or section, typically containing information about the author, copyright data, or links to related documents.
<header>: Represents introductory content, typically a group of introductory or navigational aids.
<main>: Represents the dominant content of the <body> of a document. The main content area consists of content that is directly related to or expands upon the central topic of a document.
<mark>: Represents text which is marked or highlighted for reference or notation purposes.
<nav>: Defines a section of navigation links.
<section>: Defines a standalone section of functionality contained within an HTML document, typically with a heading, that doesn’t have a more specific semantic element to represent it.
<time>: Represents a specific period in time, such as a timestamp on a blog post.

Using semantic HTML makes your HTML more readable for developers. It clearly communicates the structure and meaning of your content. It also helps assistive technologies, like screen readers, to better interpret your pages.

Search engines also use semantic information to better understand the roles and relative importance of the different parts of your webpage. So using semantic HTML can indirectly benefit a website’s search engine optimization (SEO).

HTML and SEO

While search engines are getting better at understanding the content of a webpage, they still rely heavily on the HTML structure to determine the importance and context of different elements on the page. This is where semantic HTML and proper tag usage become crucial for SEO.

Here are some ways HTML affects SEO:

Headings: Search engines use the headings (<h1> to <h6>) to understand the structure and main topics of your content. The <h1> tag should generally be used for the main title of the page, with <h2> to <h6> used for subheadings.
Page Title and Meta Description: The <title> tag and the <meta> description tag provide information that often appears on the search engine results page (SERP). A concise, descriptive title and meta description can improve click-through rates from the SERP.
Structured Data: You can use certain HTML tags and attributes to provide explicit clues about the meaning of a page to search engines. When used with formats like Schema.org, this structured data can enable special features in search results, like review stars, recipe information, or event details.
Alt Text for Images: The alt attribute provides a text description of an image. This helps search engines understand what the image is about, which they can use for both indexing the image and understanding the content of the page.
Internal Linking: Linking to other relevant pages on your site using descriptive anchor text can help search engines understand the structure and content of your site.
Page Speed: While not directly related to HTML, the size and complexity of your HTML can affect your page’s loading speed, which is a factor in search engine rankings.

By using HTML tags effectively and providing clear, structured content, you can significantly improve your website’s SEO. However, remember that HTML is just one part of the SEO puzzle. Quality content, performance optimizations, and other factors are also critical for good search engine rankings.

HTML Best Practices

Writing clean, semantic, and standards-compliant HTML can make your websites more accessible, performant, and maintainable. Here are some best practices to follow:

Use Semantic Elements: Always use the most appropriate semantic element for the content. This makes your HTML more meaningful and helps with accessibility and SEO.
Keep Your Code Clean and Readable: Indent nested elements consistently and use meaningful names for class and id attributes. This makes your code easier to read and maintain.
Avoid Divitis: “Divitis” is a term for overusing <div> elements. While <div> has its uses, try to use more specific semantic elements when possible.
Validate Your HTML: Use tools like the W3C Markup Validation Service to check that your HTML is error-free and follows the standards.
Optimize for Performance: Keep your HTML lean and minimize the use of complex, nested structures. This can help with page load times.
Use Alt Text for Images: Always provide descriptive alt text for images. This is important for accessibility (for users with screen readers) and for SEO.
Separate Content from Style and Behavior: Use HTML for content and structure, CSS for presentation, and JavaScript for behavior. Avoid inline styles and script where possible.
Use Relative URLs: When linking to other pages or resources on your own site, use relative URLs. This makes your site more portable.
Declare the Document Type and Language: Always start your HTML document with the <!DOCTYPE html> declaration and include the lang attribute on the <html> tag to specify the language of the page.
Test on Different Browsers and Devices: Make sure your HTML works as expected across different browsers and devices, including mobile devices.

By following these best practices, you can create HTML that’s more robust, manageable, and provides a better user experience.

HTML and Web Development

HTML is the cornerstone of web development. It provides the structure and content for web pages, which CSS and JavaScript then enhance and interact with.

Here’s how HTML typically fits into the web development process:

Planning: Before writing any code, the structure and content of the website are planned out. This might involve creating wireframes, content strategies, and information architecture diagrams.
HTML Development: With the plan in place, developers start writing the HTML code. They create the basic structure of the page with semantic elements and add the textual content.
CSS Styling: After the HTML is written, developers use CSS to style the page. This involves selecting HTML elements and applying styles to them, such as colors, fonts, spacing, and layout.
JavaScript Interaction: Developers use JavaScript to add interactivity to the page. This could involve things like form validation, dynamic content updates, or interactive maps.
Backend Integration: Many websites also involve a backend, such as a database to store and retrieve data. HTML forms the interface through which users interact with this backend.
Testing and Deployment: Before a website is deployed, it’s thoroughly tested to ensure it works as expected on different devices and browsers. Once tested, it’s uploaded to a web server and made accessible to users over the internet.

HTML is often the first language that new web developers learn, as it’s essential for creating web content. However, modern web development usually involves a variety of other technologies and frameworks, such as:

CSS preprocessors (like Sass or Less)
JavaScript libraries and frameworks (like React, Angular, or Vue)
Server-side languages (like PHP, Python, or Node.js)
Databases (like MySQL, MongoDB, or PostgreSQL)
Version control systems (like Git)
Build tools and task runners (like Webpack, Gulp, or Grunt)

Despite the proliferation of these tools and technologies, HTML remains at the core of the web. Every website, at its most basic level, is represented by HTML code.

HTML and the Future of the Web

As the web continues to evolve, so does HTML. The most recent major version, HTML5, brought many new features and capabilities that enable more dynamic, interactive, and semantic websites and applications.

Some key areas where HTML is driving the future of the web include:

Progressive Web Apps (PWAs): PWAs are web applications that use modern web capabilities to deliver an app-like experience to users. HTML5 features like the App Cache, Web Workers, and Service Workers are key to enabling PWAs.
Mobile Web: With the increasing prevalence of mobile devices, having a mobile-friendly website is more important than ever. HTML5 introduced features like the <viewport> meta tag and new input types that make it easier to create mobile-optimized websites.
Accessibility: HTML plays a crucial role in web accessibility. By using semantic elements and following accessibility best practices, developers can create websites that are more accessible to users with disabilities.
Virtual and Augmented Reality: HTML is also being used in virtual and augmented reality applications. Libraries and frameworks like A-Frame and AR.js use HTML and JavaScript to create immersive VR and AR experiences right in the web browser.
Web Components: HTML Custom Elements, a key part of the Web Components standards, allow developers to define their own custom HTML tags. This enables more modular, reusable code.