How are plugins in the WordPress plugin directory ranked?

By fiat. The rankings are simply determined by the parent company, Automattic. It is not an algorithm. There may - in fact - be an algorithm, but it's directly manipulated.

Additionally, Automattic culls reviews they don't like. For instance, there are many 1 star ratings of Gutenberg that have been removed. My review, for instance, was suppressed.

I offer that this is illegal and a gross anti-trust violation. It could be the biggest anti-trust issue on the internet. Any lawyers here?

(bumping this as it's one of the first results in google for plugin directory seo)

The way it all works has actually come to light with the new plugin archive. The search algorithm uses Elastic Search and the weighting factors are open-source.

The main quick win factors to consider: does the search keyword exist in all your main content areas, i.e the excerpt, description, tags, authors.

Then next you should consider:

• rating
• support threads closed
• active installs

Plugins will lose rank if they haven't been updated within 180 days or within the last 0.4 WP versions.

This tool https://harlanzw.com/wpa/ will show you what you can do to improve your rank. (I am the author of this tool)

This articles goes into good full detail on how it works: https://freemius.com/blog/seo-on-new-plugin-repository/

By default the plugins are ranked by "relevance" and the only people who know how that algorithm is weighted work for wordpress.org (it's doubtful they are going to let anyone in on it).

Downloads and rating are not the main components, just one of many including keywords, date, and how many beers you buy Otto.

You don't have any options to rank high outside using the right words to describe and tag your plugin and creating a good plugin that people like.