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.

Zoom Search Engine - Add search to your website, Optical Character Recognition* (OCR) for images and PDF, Huge indexing optimizations Multi-threaded Offline Indexing

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.

A1 Website Search Engine - Create search engines for online and offline website content.

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.

Apisearch - Apisearch official website.