What is HTML?
Complete guide to the HTML file format
What is it?
HTML (HyperText Markup Language) is the standard markup language for creating web pages and web applications. Created by Tim Berners-Lee at CERN in 1991, HTML defines the structure and content of a web page using a system of tags and attributes enclosed in angle brackets. Every web page you visit is built on an HTML document that your browser interprets and renders as a visual page.
HTML documents are plain text files with the .html or .htm extension. They contain elements like headings, paragraphs, links, images, tables, forms, and embedded media, defined by start and end tags. Modern HTML5 (standardized in 2014) added native support for audio, video, canvas drawing, semantic structural elements, and offline capabilities. HTML works together with CSS for styling and JavaScript for interactivity to form the three foundational technologies of the web.
Technical Specifications
Pros & Cons
Advantages
Every web browser on every device can render HTML without any plugins or software.
Plain text format that can be read and edited in any text editor.
The HyperText part of HTML enables the linking between pages that is fundamental to the web.
Developed as an open, royalty-free standard by W3C and WHATWG with no licensing requirements.
Disadvantages
HTML alone produces unstyled, visually basic pages - presentational design requires CSS.
HTML is a markup language, not a programming language. Business logic and interactivity require JavaScript or server-side languages.
Older or non-standard browsers may render HTML differently, requiring careful cross-browser testing.
HTML requires opening and closing tags for most elements, making documents verbose compared to Markdown or plain text.
When to Use It
Here are the most common situations where HTML is the right choice:
Web Pages
Every page on the World Wide Web is an HTML document. HTML is the universal format for all web content.
Web Application Interfaces
HTML5 forms the structural layer of web applications including single-page apps and progressive web apps.
Email Templates
HTML is used for formatted emails in email clients that support rich text.
Documentation and Ebooks
HTML is used as the source format for many ebook standards including EPUB, which packages HTML pages in a zip archive.
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What is the difference between HTML and a website?
A website consists of one or more HTML pages along with CSS, JavaScript, images, and other assets served by a web server. HTML is the document format; a website is the collection of files and the server that delivers them.
Is HTML a programming language?
No. HTML is a markup language that defines document structure and content. Programming languages like JavaScript execute logic; HTML only marks up text content with structural meaning.
What is the difference between .html and .htm?
They are identical formats. The .htm extension was used in early Windows systems that required 3-character extensions. Both extensions work identically in all browsers and web servers.
What is HTML5?
HTML5 is the fifth major version of HTML, standardized in 2014. It added native audio and video elements, canvas drawing, web storage, semantic elements (header, nav, article, footer), and many other modern web capabilities.
Can I open an HTML file without the internet?
Yes. HTML files are local documents that your browser can open from your hard drive using File > Open or by dragging the file into the browser window.