HTML (HyperText Markup Language) is the standard markup language used to create web pages. It defines the structure and semantic meaning of content, headings, paragraphs, links, images, lists, forms, and other elements, using tags wrapped in angle brackets. HTML is one of the three core technologies of the web alongside CSS (for visual styling) and JavaScript (for interactivity).

The current standard is HTML5, an evolving specification maintained by WHATWG (Web Hypertext Application Technology Working Group).

Basic structure

A minimal HTML document:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Page title</title>
</head>
<body>
  <h1>Welcome</h1>
  <p>This is a paragraph.</p>
</body>
</html>

Each component:

<!DOCTYPE html>, declares the document type
<html>, root element
<head>, metadata, links to stylesheets, scripts, page title
<body>, visible content
<h1>, <p>, content elements

Common HTML elements

Element	Purpose
`<h1>` to `<h6>`	Headings (six levels)
`<p>`	Paragraph
`<a>`	Hyperlink
`<img>`	Image
`<ul>`, `<ol>`, `<li>`	Lists (unordered, ordered, item)
`<table>`, `<tr>`, `<td>`, `<th>`	Tables
`<form>`, `<input>`, `<button>`, `<select>`, `<textarea>`	Form controls
`<div>`	Generic container with no semantic meaning
`<span>`	Generic inline container
`<header>`, `<footer>`, `<nav>`, `<main>`, `<article>`, `<section>`, `<aside>`	Semantic structural elements
`<video>`, `<audio>`	Media
`<svg>`	Scalable vector graphics
`<canvas>`	Drawing surface for JavaScript
`<script>`	JavaScript code or reference
`<link>`	External resource (typically stylesheets)
`<meta>`	Metadata (character set, viewport, descriptions)

Semantic HTML

HTML elements are not just visual containers, they convey meaning. Semantic HTML uses elements according to their intended purpose:

A <button> indicates an interactive control
A <nav> indicates a navigation section
An <article> indicates self-contained content
A <header> indicates introductory content

Semantic markup matters for:

Accessibility. Screen readers and assistive technologies rely on semantic meaning
SEO. Search engines use structural elements to understand page content
Maintainability. Code is easier to read and modify when its purpose is explicit
Browser features. Some elements have built-in behavior (e.g., <details> collapses by default)

Using <div> for everything (sometimes called “div soup”) loses these benefits.

HTML attributes

Attributes provide additional information about elements:

<a href="https://example.com" target="_blank" rel="noopener">Link</a>
<img src="photo.jpg" alt="A descriptive caption" width="600" height="400" />
<input type="email" name="email" required placeholder="Your email" />

Common attributes:

id, unique identifier
class, one or more class names for CSS or JavaScript targeting
href, link destination
src, source for images, scripts, iframes
alt, alternative text for images
title, tooltip text
data-*, custom data attributes for application use
aria-*, accessibility attributes
style, inline CSS (generally avoided in favor of stylesheets)

How HTML is processed

When a browser receives an HTML document:

It parses the HTML into a Document Object Model (DOM) tree
It fetches and applies linked stylesheets and scripts
It computes layout and renders the visible page
It executes JavaScript that modifies the DOM
It responds to user interactions, updating the DOM as needed

JavaScript can read and modify the DOM, enabling interactive behavior.

HTML versions

Version	Released	Notes
HTML 1.0	1993	Initial public version
HTML 4.01	1999	Long-running standard
XHTML 1.0	2000	Stricter, XML-based variant
HTML5	2014	Major modernization; new elements, APIs
HTML Living Standard	Ongoing	Continuously updated by WHATWG

The current state of HTML is best described as a Living Standard maintained by WHATWG; “HTML5” is sometimes used to refer to the broader modern web platform including new APIs.

HTML beyond the browser

HTML is also used:

In emails. Email clients render a subset of HTML for formatted email
In RSS and Atom feeds. Article content is often HTML
In ebooks. EPUB format uses XHTML
In offline documentation. Many documentation tools generate HTML
In static site generators. HTML is the output format
In server-rendered applications. Most server-side frameworks produce HTML

Validating HTML

HTML can be validated against the specification using:

W3C Markup Validator, official validator
Browser DevTools, Chrome, Firefox highlight some issues in the inspector
Editor extensions, most code editors validate HTML in real time
Linters, automated tools (htmlhint, ESLint with HTML plugins)

Valid HTML is more reliably rendered by all browsers and assistive technologies; invalid HTML often works but may behave inconsistently.

Common misconceptions

“HTML is a programming language.” HTML is a markup language; it describes structure but does not perform computation. JavaScript is the programming language used in browsers.
“You need to learn HTML to make a website.” Many platforms (Squarespace, Wix, WordPress with page builders) generate HTML for users; learning HTML is needed for direct control or custom-coded sites.
“HTML is obsolete.” HTML is the foundation of every web page; the standard continues to evolve.
“Semantic HTML is just for screen readers.” It also affects SEO, code clarity, and behavior of assistive technologies, search bots, and browser features.