Yacy

YaCy is a full‑stack search engine that runs as a self‑hosted server, providing a web interface for querying and managing a searchable index as a built‑in web crawler with scheduling. It can be deployed on a single machine for personal or intranet use, offering a private alternative to commercial enterprise search solutions and allowing custom search pages to be embedded in other web applications.

The software can also join a peer‑to‑peer network in which each YaCy instance exchanges index data with other peers, creating a decentralized search cluster that users can tap into without a central authority. Users may disable the P2P mode or restrict individual searches to the local index, making the system adaptable to privacy‑focused scenarios.

YaCy is released under GPL‑2.0, requires Java 11 or later, and can be built from source, installed via pre‑compiled packages, or run from an official Docker image. The project is stable, open‑source, and free of subscription fees.