Chrome's Reader Mode engine, whose content-extraction heuristics are a public proxy for how machines separate main content from boilerplate.
DomDistiller is the engine behind Chrome's Reader Mode, and it's a valuable, open proxy for how a sophisticated Google system decides what on a page is real content versus boilerplate. Reverse-engineering it tells you a lot about machine readability.
It works as a multi-stage heuristic pipeline over the rendered DOM (not the raw HTML). It segments the page into text blocks, discards hidden elements, then scores each block: high link density is penalised as navigation or footer; substantial continuous text scores well; semantic tags like <article>, <p> and <blockquote> are positive while <nav>, <aside> and <footer> are negative; and a blacklist of class/ID substrings (comment, ad, share, sidebar, promo, related) further demotes non-content.
The lesson for technical SEO is that clean semantic structure and low boilerplate help machines isolate your main content — the same content that then gets fed to AI systems. It's a close relative of the content fetcher and the structured page representation behind Annotated Page Content.
