The Document Object Model (DOM) is an interface that exposes document structure programmatically to developers. Perhaps the most common application of the DOM is “Dynamic HTML” (DHTML), where an HTML document can be modified programmatically within the browser using an embedded scripting language. Typically, the scripting language is some flavor of ECMAScript (such as JavaScript or JScript), since most browsers support it, but others can be used as well. (For browsers on Windows, this can even be Python!) This allows you to change the background color of a table cell, or dynamically change font faces after the page is in the browser. The DOM defines the interface for vendors to offer compatible APIs.

The DOM is also extremely useful when exposed by a library such as the Python Standard Library or PyXML. It can allow you to use Python to manipulate an XML document already in memory. With the DOM interfaces, you can either change or extract portions of the document.