WordPress search doesn’t search everything, and doesn’t give you enough control over what is searched and how. Relevanssi gives you full access and full control, with plenty of filters and ways to make Relevanssi work the way you want your search to work.
Relevanssi Search WordPress plugin is absolutely the best search plugin out there! I’ve started using it on my busy boxing site since 2011 (six years ago). It is incredibly fast, full of useful granular options (weighted searches, custom excerpt length, logical exclusions), full of features (highlighted terms, synonyms, stop words, partial searches, WPML-compatibility), and more. The UI is clean and easy to understand/use and the code is absolute no-nonsense. The plugin’s logic is so clever and comprehensive, it has and continues to blow away the competition throughout all these years. What makes Relevanssi even better is Mikko’s dedication and top-notch customer service. I can’t say enough about this amazing search plugin. I recommend everyone to do what I do and pay for the “Permanent” lifetime plan because nobody else will ever come close to the features and ease-of-use of Relevanssi.