Yoast SEO is the more common of the two in our index: it runs on 3,876 websites against 4 for Newspack, and 4 sites use both. Counts come from real scans, not vendor claims.
Newspack is an open-source publishing platform built on WordPress for small to medium sized news organizations. It is an “opinionated” platform that stakes out clear, best-practice positions on technology, design, and business practice for news publishers.
Yoast SEO is a search engine optimisation plugin for WordPress and other platforms.
4 sites run both Newspack and Yoast SEO. That is 100% of the sites using Newspack, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.