Pronounced "ya see," YaCy is a search engine utility, built on peer-to-peer network (P2P) design. The core program is built with Java and is installed on a computer. Each computer, called a YaCy-peer, crawls the Internet and indexes web pages it finds. The indexing is stored in a common database that is accessible and shared among all YaCy-peers using P2P.
As of September 2006, there were several hundred YaCy-peers, working to increase and improve the YaCy search engine results and accuracy. The search engine is based on four elements: crawler, indexer, search, and administration interface and data storage. YaCy does not have a central server, like most other search engines, which allows it to remain uncensored and theoretically more reliable. YaCy is not owned by any individual or company, which keeps it free of centralized advertising. It also helps the search engine to attain a higher level of privacy. However, YaCy uses HTTP requests to function properly, which may cause it to be slower than other search engines.