HTML

in English: HyperText Markup Language (HTML)

basicwidespread

HTML is the basic language of websites: it uses tags to mark what is the heading, paragraph, image, or link on a page.

In plain terms

Imagine a newspaper editor marking a manuscript with a pencil: this will be the headline, this the caption, the photo goes here. HTML does the same for websites. It does not write the text but specifies which part is what.

The markup elements are called tags and are placed between angle brackets. Your browser reads them and renders the page accordingly: large-type headings, paragraphs, clickable links, forms.

HTML provides the skeleton by itself. CSS adds the colors, fonts, and layout, while JavaScript handles interactive functions, such as what happens when a button is pressed. It is like a house: HTML is the walls and rooms, CSS is the paint and furniture, and JavaScript is the electricity and plumbing.

In the AI era, it has come back to the forefront because language models and AI agents read HTML when processing web pages and write HTML when creating web pages for you.

How it works

The website creator (human or AI) writes a text file where content is placed between tags, for example, the main title between <h1> and </h1>.
When you open a web address, your browser downloads this file from the server.
The browser reads the tags and builds a tree-like internal structure from them: what belongs under what, what follows what.
It adds the appearance defined in CSS and the behavior written in JavaScript, then renders the finished page on the screen.
Search engines, screen readers, and AI agents read this same structure, so it matters that tags accurately label what is what.

An everyday example

You ask an AI chatbot to create a simple landing page for your business. You receive a file ending in .html; double-clicking it displays the finished page in your browser. If you right-click in the browser and select "View Page Source," you can inspect the HTML code of any website.

Who is affected

everyoneEvery website you open is built from HTML, and so is most formatted email.

developerIt is the basis of web work, and the HTML written by coding agents must be checked by you. → Code

marketerThe appearance of newsletters and landing pages, as well as the results of search engine optimization, largely depend on whether the HTML is proper. → Marketing

entrepreneur, executiveYour company website is understood—or misunderstood—by search engines and AI agents through the HTML.

A common misconception

MythHTML is a programming language, and anyone who writes HTML is a programmer.

In realityHTML is a markup language: it describes what is on the page but does not calculate, decide, or execute instructions. Logic is added by other languages, most notably JavaScript.

Limits and risks

HTML alone does not make a page look good or function; CSS and usually JavaScript are also needed.
AI-generated HTML may look good at first glance, yet it can contain errors: poor structure, missing image descriptions, or layouts breaking on mobile.
Hidden, invisible text embedded in a page's code can deceive an AI agent reading the page (this is one form of prompt injection).
An HTML file or HTML attachment from an unknown source may hide a phishing page, so do not enter your password on such a page.

Similar, but not the same

CSS – HTML specifies what is on the page, while CSS defines how it should look.
JavaScript – JavaScript is a real programming language that controls page behavior, while HTML only describes content and structure.
Markdown – Markdown is a simple markup that is easy for humans to read and is often converted to HTML; AI chatbots also mostly reply in it.

Related concepts

Broader

Markup Language, Web development, World Wide Web

Narrower

HTML5, HTML tag, Form

On the edge

CSS, JavaScript, Markdown, Browser, XML

A brief history

Tim Berners-Lee, a British scientist, developed HTML at the CERN research center in Geneva as part of the creation of the World Wide Web, between 1989 and 1991. HTML5 became an official W3C recommendation in 2014. Since 2019, the language has been maintained by the WHATWG, founded by browser manufacturers, as a continuously updated "living standard" (HTML Living Standard).

Where things stand

Even at the end of 2026, HTML is the indispensable foundation of the web, and every browser displays it. Language models and coding agents write more and more HTML, and AI agents that browse the web independently read more and more of it.

Status: 2026 November

Also known as

HTML · HyperText Markup Language · Hypertext Markup Language · HTML5 · hypertext markup language · HTML code · HTML-oldal · html

Sources

This entry was machine-edited and has undergone machine expert review; the “In the news” section updates automatically from Agent Age stories.