Structure survives
Headings become ATX headings, lists stay lists, code blocks are fenced, and HTML tables become GitHub Flavored Markdown pipe tables rather than flattened text. Relative links and images are rewritten as absolute URLs, so the Markdown still points at the right place once it leaves the site it came from. A page whose title lives outside the article gets it back as an H1.
Chrome is a heuristic
“Main content” means the page’s <article>, else <main>, else an element marked role="main", with <nav> and <aside> removed. On a page that lists many articles the widest container wins instead. If the guess is wrong, convert the whole page — you get everything in <body> minus the noise above.
Client-rendered pages
The fetcher reads the HTML a server sends; it does not run JavaScript. A page that draws its content in the browser after loading will come back nearly empty. Open it, copy what you see, and paste it into HTML to Markdown instead.