This is the YaCy Search Engine application and the main git repository for
Java HTML JavaScript CSS XSLT Shell Other
Latest commit 8d790ab Jan 21, 2017 @reger24 reger24 delete outdated and unmaintained Netbeans project
Netbeans has good build-in maven support which is a supported and 
maintained build env, making special and additional NB setting obsolete.
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.settings removed warnings May 13, 2014
addon release 1.92 Dec 26, 2016
bin Changes to improve compatibility with OpenBSD. (see Feb 23, 2015
debian Set more generic java runtime dependencies. May 27, 2016
defaults added luccioman development release builds as discussed in Dec 26, 2016
dictionaries changed way to integrate dictionary files: Sep 2, 2009
docker Upgraded Apache Ant to 1.10.0 for the Alpine flavor Docker image. Jan 2, 2017
examples move example code SearchClient out of yacycore package Mar 14, 2016
htroot upd to commons-compress-1.13.jar Jan 20, 2017
langdetect Use language-detection library for increased accuracy Jul 2, 2015
lib fix the missing solr-5.5.2.jar delete from prev. commit Jan 20, 2017
libbuild Upgraded jgit build library to version 4.5.0 Jan 4, 2017
libt update to JUnit 4.11 Jul 6, 2014
locales Start to rename "Augmented Browsing" to "Web Proxy ..." / "View via P… Jan 12, 2017
skins correct the dark themes to show also a dark navbar on searchresults Jun 4, 2015
source Added an optional parameter to webstructure.xml api. Jan 19, 2017
test Updated Javadoc and Junit tests for the WebStructureGraph class. Jan 17, 2017
vocabularies moved yacy.logging to defaults according to request in May 17, 2012
.checkstyle problems with code style Jun 29, 2009
.classpath upd to solr-5.5.3 Jan 20, 2017
.env Removed unnecessary variables for local heroku run Jul 12, 2016
.gitignore Ignore generated Javadoc with git SCM. Jan 9, 2017
.project Update .project May 8, 2016
.travis.yml Create .travis.yml Nov 9, 2015
AUTHORS added flori and me Jun 13, 2008
COPYRIGHT updated copyright message; included LGPL for 'cora' and a warranty Jun 30, 2013 Simplified Heroku variables configuration Jul 28, 2016
NOTICE * updated jxpath to latest v1.3 Jul 15, 2009
Procfile Simplified Heroku variables configuration Jul 28, 2016 Fixes #16 Updates documentation about cloning and build from source Oct 27, 2016
app.json Fixed description small typing errors. Aug 10, 2016
assembly.xml Fixed maven assembly base directory to match last main YaCy binaries. Jan 9, 2017
build.nsi Changed Windows Firewall Rules to just honor the default Port 8090, but May 28, 2014 release 1.92 Dec 26, 2016
build.xml upd to solr-5.5.3 Jan 20, 2017
getWin32MaxHeap.bat update for memory observer algorithm Dec 6, 2009
gpl.txt initial load with yacy 0.36 Apr 7, 2005
installYaCyWindowsService.bat upd classpath in batches (remove not necessary htroot) Feb 3, 2016 Fix for Aug 25, 2014
lgpl21.txt migrated all my LGPL 3 -licensed files to the LGPL 2.1 because LGPL 3… Jun 28, 2010
pom.xml upd to solr-5.5.3 Jan 20, 2017 Fix for Aug 25, 2014
startYACY.bat upd classpath in batches (remove not necessary htroot) Feb 3, 2016 Fixed docker stop behavior. Dec 31, 2016
startYACY_debug.bat harmonize classpath with startYaCy.bat Feb 28, 2016
stopYACY.bat upd classpath in batches (remove not necessary htroot) Feb 3, 2016 Fix for Aug 25, 2014
uninstallYaCyWindowsService.bat added Windows Service installer Dec 26, 2013 Fix for Aug 25, 2014
yacy-packages.readme added documentation for new yacy package structure Oct 20, 2009
yacy.yellow performance setting for remote indexing configuration and latest chan… Jul 22, 2005


Deploy to Docker Cloud Deploy

What is this?

YaCy is a search engine software. It takes a new approach to search because it does not use a central server. Instead, its search results come from a network of independent peers. In such a distributed network, no single entity decides what gets listed, or in which order results appear.

The YaCy search engine runs on each user's own computer. Search terms are hashed before they leave the user's computer. Different from conventional search engines, YaCy is designed to protect the users' privacy. A user's computer can create with YaCy its individual search indexes and rankings, so that results better match what the user is looking for over time. YaCy also makes it easy to create a customized search portal with a few clicks.

Each YaCy user is either part of a large search network (YaCy contains a peer-to-peer network protocol to exchange search indexes with other YaCy search engine installations) or the user runs YaCy to produce a personal search portal that can be either public or private.

YaCy search portals can also be placed in intranet environment which makes YaCy a replacement for commercial enterprise search solutions. A network scanner makes it easy to discover all available http, ftp and smb servers.

To create a web index, YaCy has a web crawler for everybody, without censorship and central data retention:

  • search the web (automatically using all other YaCy peers)
  • co-operative crawling; support for other crawlers
  • intranet indexing and search
  • set up your own search portal
  • all users have equal rights
  • comprehensive concept to anonymise the users' index

To be able to perform a search using the YaCy network, every user has to set up their own node. More users are leading to higher index capacity and better distributed indexing performance.


YaCy is published under the GPL v2 The source code is inside the release package (see /source and /htroot).

Where is the documentation?

Documentation can be found at:

Every of these locations has a (YaCy) search functionality which combines all these locations into one search result.

Dependencies? What other software do I need?

You need java 1.7 or later to run YaCy, nothing else. Please download it from

YaCy also runs on IcedTea7. See

NO OTHER SOFTWARE IS REQUIRED! (you don't need apache, tomcat or mysql or whatever)

How do I start this software?

Startup and Shutdown of YaCy:

  • on GNU/Linux and OpenBSD: to start: execute ./ to stop : execute ./

  • on Windows: to start: double-click startYACY.bat to stop : double-click stopYACY.bat

  • on Mac OS X: please use the Mac Application and start or stop it like any other Mac Application (doubleclick to start)

How do I use this software, where is the administration interface?

YaCy is a build on a web server. After you started YaCy, start your browser and open


There you can see your personal search and administration interface.

What if I install YaCy (headless) on a server?

You can do that but YaCy authorizes users automatically if they access the server from the localhost. After about 10 minutes a random password is generated and then it is not possible to log in from a remote location. If you install YaCy on a server that is not your workstation, then you must set an administration account immediately after the first start-up. Open:


and set an administration account.

Can I run YaCy in a virtual machine or a container?

YaCy runs fine in virtual machines managed by software such as VirtualBox or VMware.

Container technology may be more flexible and lightweight and also works fine with YaCy.

These technologies can either be deployed locally, on remote machines you own, or in the 'cloud'. Decide what fits the most your privacy requirements.


Deploy easily YaCy on a Docker cloud provider of your choice (can be a machine you own) with the deploy button at the top of this page.

More details for YaCy with Docker in docker/


Deploy easily on Heroku PaaS (Platform as a service) provider using the deploy button at the top.

More details for YaCy on Heroku in

Port 8090 is bad, people are not allowed to access that port

You can forward port 80 to 8090 with iptables: iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8090 On some operation systems, you must first enable access to the ports you are using like: iptables -I INPUT -m tcp -p tcp --dport 8090 -j ACCEPT

How can I scale this; how much ram is needed; disk space?

YaCy can scale up to many millions of web pages in your own search index. The default assignment of RAM is 600MB which is assigned to the java process but not permanently used by it. The GC process will free the memory once in a while. If you have a small index (i.e. about 100000 pages) then you may assign less memory (i.e. 200MB) but if your index scales up to over 1 million web pages then you should start to increase the memory assignment. Open http://localhost:8090/Performance_p.html and set a higher/lower memory assignment. If you have millions of web pages in your search index then you might habe gigabytes of disk space allocated. You can reduce the disk space i.e. setting the htcache space to a different size; to do that open http://localhost:8090/ConfigHTCache_p.html and set a new size.

Join the development!

YaCy was created with the help of many. About 30 programmers have helped, a list of some of them can be seen here: Please join us!

How to get the source code and how to compile YaCy yourself?

The source code is inside every YaCy release. You can also get YaCy from by cloning the repository

git clone

Please clone our code and help with development! The code is licensed under the GPL v2.

Compiling YaCy:

  • you need Java 1.7 or later and Apache Ant
  • just compile: "ant clean all" - then you can "./" or "./startYACY.bat"
  • create a release tarball: "ant dist"
  • create a Mac OS release: "ant distMacApp" (works only on a Mac)
  • create a debian release: "ant deb"
  • work with eclipse: within eclipse you also need to start the ant build process because the servlet pages are not compiled by the eclipse build process after the dist prodecure, the release can be found in the RELEASE subdirectory

Are there any APIs or how can I attach software at YaCy?

There are many interfaces build-in in YaCy and they are all based on http/xml and http/json. You can discover these interfaces if you notice the orange "API" icon in the upper right of some web pages in the YaCy web interface. Just click on it and you will see the xml/json version of the information you just have seen at the web page. A different approach is the usage of the shell script provided in the /bin subdirectory. The just call also the web interface pages. By cloning some of those scripts you can create more shell api access methods yourself easily.


Our primary point of contact is the german forum at There is also an english forum at We encourage you to start a YaCy forum in your own language.

If you have any questions, please do not hesitate to contact the maintainer: Send an email to Michael Christen ( with a meaningful subject including the word 'yacy' to prevent that your email gets stuck in my anti-spam filter.

If you like to have a customized version for special needs, feel free to ask the author for a business proposal to customize YaCy according to your needs. We also provide integration solutions if the software is about to be integrated into your enterprise application.

Germany, Frankfurt a.M., 26.11.2011 Michael Peter Christen