HTML Parser

An HTML parser is a tool or library that reads HTML markup and builds a structured, queryable representation (typically a DOM tree) from which specific elements can be extracted. Parsers make it possible to pull product prices, property details, or table rows from raw HTML text.

Popular parsing libraries include Beautiful Soup and lxml in Python, Cheerio in JavaScript, and Nokogiri in Ruby. Each exposes methods to select elements by CSS class, ID, tag name, or XPath expression, then extract their text or attributes.

HTML parsing is the extraction layer in a scraping pipeline - and the most fragile part. Parsers break whenever the target website changes its HTML structure. This maintenance burden is one of the core arguments for using data APIs instead of building and maintaining custom scrapers.