YaCy
Search engines normally rent you answers from an index you cannot inspect; YaCy installs the entire machine on your server: the crawler, the index, the ranking, and the search page itself. Run it as a public web search portal with faceted results, topic clouds, and image search, or point the crawler at your intranet where a network scanner discovers HTTP, FTP, and file servers for a private enterprise search. Expert crawl jobs take start URLs, sitemaps, or link lists with depth limits, per-domain caps, and freshness rules, and the scheduler keeps re-crawling so results stay current. Peers exchange index data over a built-in peer-to-peer protocol, so a fresh installation can answer from the shared network index before its own crawl has seen much of the web. Private modes cut that connection for local-only answers computed on your hardware alone. The index browser walks stored hosts and draws link graphs of what the crawler found. Every page in the interface has an XML or JSON twin for automation, and the portal design tools restyle the result page for embedding in your own site. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-2.0 licensed.
Deploy