Content Upgrade
A lead magnet made for one specific page: a checklist, template, or extended version of the article the visitor is already reading, offered for an email.
A content upgrade is a lead magnet scoped to a single piece of content rather than the whole site. A post about welcome email sequences might offer the five templates it describes as a downloadable file. The visitor has already shown interest in that exact topic, so the offer needs no persuasion beyond stating what it is.
Good content upgrades are direct extensions of the page: the spreadsheet behind the analysis, a printable version of the checklist, the swipe file of examples, or a longer edition with extra sections. A generic ebook offered on every page is not a content upgrade, it is a site-wide lead magnet with the same relevance problem everywhere.
Delivery is usually a popup opened from an inline link or button in the article (a click trigger), which means the visitor asked to see it. That makes a content upgrade one of the few cases where a centered modal is welcome mid-read. Use URL targeting so each upgrade appears only on its own page, and send the file immediately after submission.
See it in practice