Dynamic HTML, or DHTML, is a term which was used by some browser vendors to describe the combination of HTML, style sheets and client-side scripts (JavaScript, VBScript, or any other supported scripts) that enabled the creation of interactive and animated documents. 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, Python, JSP or ASP.NET) where the web server generates content before sending it to the client.

DHTML is the predecessor of Ajax and DHTML pages are still request/reload-based. Under the DHTML model, there may not be any interaction between the client and server after the page is loaded; all processing happens on the client side. By contrast, Ajax extends features of DHTML to allow the page to initiate network requests (or 'subrequest') to the server even after page load to perform additional actions. For example, if there are multiple tabs on a page, the 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.