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.
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.
Apache Solr - Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and...
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.
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.
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.