Relevanssi Premium is the premium version of Relevanssi, a popular search plugin with over 80,000 active installations. Both versions of Relevanssi make your search results more relevant, so that the best results appear first. They also expand the searchable content to cover custom fields, categories, tags and other taxonomy terms, excerpts, authors and pretty much whatever you want.
Relevanssi Premium adds more, making multisite searches possible. Search on one site, get results from all the sites in the network! Premium can also find user profiles and taxonomy term pages. Relevanssi Premium also has very good “Did you mean?” suggestion feature.
With Relevanssi, you have total control over your search, as the plugin is armed with filters that let you reorganize, sort, and filter the search results as you wish. You can adjust the posts on the fly before they are indexed.
There are some limits to what Relevanssi Premium can do. It can index attachment titles and descriptions, but not the contents of PDF files or other documents. It is also designed for fairly small scale: it’s fine for most blogs and information sites, but when the number of documents to index goes over 10.000 posts, it’s usually a good idea to consider other, more robust solutions.