What they did
In August 2022 Google announced the helpful content update and described how its classifier works.
What they found
Google called it a new site-wide signal. It said content on sites with relatively high amounts of unhelpful content is less likely to perform well, so removing unhelpful content could help the rankings of other pages. The classifier is entirely automated, using a machine-learning model.
How much weight to give it
A clear first-party statement that low-quality sections can drag down a whole site, not only the weak pages themselves. That reframes thin content as a site-level risk.
What it doesn't prove
Google folded the standalone helpful content system into its core ranking systems in March 2024, so the separate-classifier description is dated. How strictly the effect is site-wide in practice is debated among SEOs.