Dynamic HTML, or DHTML, is an umbrella term for a collection of technologies used together to create interactive and animated websites[1] by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (such as CSS), and the Document Object Model (DOM).[2] The application of DHTML was introduced by Microsoft with the release of Internet Explorer 4 in 1997.

DHTML allows scripting languages to change variables in a web page's definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load.

By contrast, a dynamic web page is a broader concept, covering any web page generated differently for each user, load occurrence, or specific variable values. This includes pages created by client-side scripting, and ones created by server-side scripting (such as PHP, Perl, JSP or ASP.NET) where the web server generates content before sending it to the client.

DHTML is differentiated from Ajax by the fact that a DHTML page is still request/reload-based. With DHTML, there may not be any interaction between the client and server after the page is loaded; all processing happens in JavaScript on the client side. By contrast, an Ajax page uses features of DHTML to initiate a request (or 'subrequest') to the server to perform additional actions. For example, if there are multiple tabs on a page, pure DHTML approach would load the contents of all tabs and then dynamically display only the one that is active, while AJAX could load each tab only when it is really needed.

Key features:-DHTML allows authors to add effects to their pages that are otherwise difficult to achieve, by changing the Document Object Model (DOM) and page style. The combination of HTML, CSS and JavaScript offers ways to:

Animate text and images in their document.

Embed a ticker or other dynamic display that automatically refreshes its content with the latest news, stock quotes, or other data.

Use a form to capture user input, and then process, verify and respond to that data without having to send data back to the server.

Include rollover buttons or drop-down menus.

A less common use is to create browser-based action games. Although a number of games were created using DHTML during the late 1990s and early 2000s,[citation needed] differences between browsers made this difficult: many techniques had to be implemented in code to enable the games to work on multiple platforms. Recently browsers have been converging towards web standards, which has made the design of DHTML games more viable. Those games can be played on all major browsers and they can also be ported to Plasma for KDE, Widgets for macOS and Gadgets for Windows Vista, which are based on DHTML code.

The term "DHTML" has fallen out of use in recent years as it was associated with practices and conventions that tended to not work well between various web browsers. DHTML may now be referred to as unobtrusive JavaScript coding (DOM Scripting), in an effort to place an emphasis on agreed-upon best practices while allowing similar effects in an accessible, standards-compliant way.

DHTML support with extensive DOM access was introduced with Internet Explorer 4.0. Although there was a basic dynamic system with Netscape Navigator 4.0, not all HTML elements were represented in the DOM. When DHTML-style techniques became widespread, varying degrees of support among web browsers for the technologies involved made them difficult to develop and debug. Development became easier when Internet Explorer 5.0+, Mozilla Firefox 2.0+, and Opera 7.0+ adopted a shared DOM inherited from ECMAScript.

More recently, JavaScript libraries such as jQuery have abstracted away many of the day-to-day difficulties in cross-browser DOM manipulation.