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.
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
Google Custom Search Engine - Google Custom Search is a platform provided by Google that allows web developers to feature specialized information in web searches, refine and categorize queries and create customized search engines, based on Google Search.
Sphinx (search engine) - Sphinx is a fulltext FLOSS search engine that provides text search functionality to client applications. Sphinx (search engine) - WikiMili, The Free Encyclopedia - WikiMili, The Free Encyclopedia
Site Search 360 - Site Search 360 enhances and improves your built-in CMS or product search with autocompletion, semantic search, filters, facets, detailed analytics, and a whole lot of customization options.