DOM

The DOM (Document Object Model) is a programming interface that represents an HTML or XML document as a tree of objects. Every element - headings, paragraphs, tables, images - is a node in the tree, and the DOM exposes methods to traverse, query, and manipulate this structure programmatically.

In web scraping, the DOM is what parsers and headless browsers operate on. A scraper selects specific DOM nodes using CSS selectors or XPath expressions, then extracts their text content or attributes to build structured data. The quality of the DOM structure on the target page directly determines how reliable the scraper can be.

Understanding the DOM is also essential for frontend developers - it is the interface through which JavaScript modifies page content in a browser. The same tree structure that powers dynamic websites is what makes headless-browser scraping possible.