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