Ajax Search Lite - WordPress Live Search plugin - Ajax search lite. A responsive live search engine for WordPress, for free.
SearchWP - Instantly improve the search experience of your WordPress site today with SearchWP, the best WordPress search plugin you can find!
Advanced Woo Search - Advanced Woo Search - WordPress ajax search plugin for WooCommerce store. Search in product title, description, excerpt, sku, tags, categories, attributes, custom fields, custom taxonomies.
Relevanssi - Relevanssi replaces the standard WordPress search with a better search engine, with lots of features and configurable options.
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
WP Rocket - WP Rocket offers a caching plugin for Wordpress.