YaCy

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YaCy

Original author(s)	Michael Christen
Developer(s)	YaCy community
Initial release	2003; 21 years ago (2003)[1]
Stable release	1.940 / 18 October 2024; 16 days ago (2024-10-18)[2][3]
Repository	github.com/yacy/yacy_search_server
Written in	Java
Operating system	Cross-platform
Size	104-113 MB
Type	Overlay network, Search engine
License	GPL-2.0-or-later
Website	yacy.net/en/

YaCy (pronounced “ya see”) is a free distributed search engine built on the principles of peer-to-peer (P2P) networks, created by Michael Christen in 2003.^[4][5] The engine is written in Java and distributed on several hundred computers, as of September 2006^{[update][needs update]}, so-called YaCy-peers.

Each YaCy-peer independently crawls through the Internet, analyzes and indexes found web pages, and stores indexing results in a common database (so-called index) which is shared with other YaCy-peers using principles of peer-to-peer. This decentralized approach ensures privacy and eliminates the need for a central server.^[6]

Compared to semi-distributed search engines, the YaCy network has a distributed architecture. All YaCy-peers are equal and no central server exists. It can be run either in a crawling mode or as a local proxy server, indexing web pages visited by the person running YaCy on their computer. Several mechanisms are provided to protect the user's privacy. Search functions are accessed by a locally run web server which provides a search box to enter search terms, and returns search results in a format similar to popular search engines.^[7]