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YaCy vs Fess: catalog facts
YaCy	Fess
Free Free and open source software.	Free Free and open source under Apache-2.0; commercial support is available.
Web, Self-hosted	Windows, macOS, Linux, Web, Self-hosted
Decentralized peer-to-peer web index with no central operator Can run as a private crawler or intranet search portal	Crawler, indexer, admin console and search UI included Indexes Office, PDF and archive files from many sources
Pre-compiled packages are not built regularly; compiling from source is recommended Peer-to-peer results are less complete than major web search engines	Non-Docker installs need a separate OpenSearch setup Requires Java 21 and server resources
Downloadable app, Self-hosted	Downloadable app, Self-hosted
Open source	Open source
License: GPL-2.0	License: Apache-2.0
No account needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.