Why your fixed header disappears in Puppeteer fullPage screenshots (and how to fix it)

I spent two evenings debugging this. Sharing so you don't have to. The problem When you call page.screenshot({ fullPage: true }) on a site with a position: fixed header, one of three things usually happens: The header renders in the middle of the page (not at the top) The header area is blank at the top of the PDF/PNG Only the first page shows the header — subsequent "pages" don't You open the site in a real browser: looks perfect. You open it in Puppeteer's viewport mode: also fine. Only fullPa