Question: What is the most popular open source software?

List of free and open-source software packages



This is a list of free and open-source software packages, computer software licensed under free software licenses and open-source licenses. Software that fits the Free Software Definition may be more appropriately called free software; the GNU project in particular objects to their works being referred to as open-source.[1] For more information about the philosophical background for open-source software, see free software movement and Open Source Initiative. However, nearly all software meeting the Free Software Definition also meets the Open Source Definition and vice versa. A small fraction of the software that meets either definition is listed here.
Some of the open-source applications are also the basis of commercial products, shown in the List of commercial open-source applications and services.
Applied fields
Artificial intelligence
General:
OpenCog – A project that aims to build an artificial general intelligence (AGI) framework. OpenCog Prime is a specific set of interacting components designed to give rise to human-equivalent artificial general intelligence.
Computer Vision:
AForge.NET – Computer Vision, Artificial Intelligence and Robotics library for the .NET Framework
OpenCV – Computer Vision Library in C++
Machine Learning:
See List of open-source machine learning software
See Data Mining below
See R programming language – packages of statistical learning and analysis tools
Planning:
TREX – Reactive planning
Robotics
ROS – Robot Operating System
YARP – Yet Another Robot Platform
CAD

FreeCAD – Parametric 3D CAD modeler with a focus on mechanical engineering, BIM, and product design
LibreCAD – 2D CAD software using AutoCAD-like interface and file format
Electronic design automation (EDA)

Fritzing
Computer simulation

Blender – 3D modeling software written in C, C++, and Python containing cloth, hair, fluid, particle, and rigid body simulation techniques
flightgear – Flight simulator written for Windows, Mac OS X, and GNU/Linux
SimPy – Queue-theoretic event-based simulator written in Python
Desktop publishing
Scribus - Designed for layout, typesetting, and preparation of files for professional-quality image-setting equipment. It can also create animated and interactive PDF presentations and forms.
Finance

Adempiere – Enterprise resource planning (ERP) business suite
Bitcoin Core – Peer-to-peer decentralised digital currency
Bonita Open Solution – Business Process Management
CiviCRM – Constituent Relationship Management software aimed at NGOs
Compiere – ERP solution automates accounting, supply chain, inventory, and sales orders
Cyclos – Software for microfinance institutions, complementary currency systems and timebanks
Dolibarr – Web-based ERP system
EOS.IO – Blockchain platform,  peer-to-peer decentralised digital currency
ERPNext – Web-based open-source ERP system for managing accounting and finance
GnuCash – Double-entry book-keeping
HomeBank – Personal accounting software
iDempiere – Business Suite, ERP and CRM
Ino erp – Dynamic pull based system ERP
jFin – Java-based trade-processing program
JFire – An ERP business suite written with Java and JDO
KMyMoney – Double-entry book-keeping
LedgerSMB – Double-entry book-keeping
metasfresh – ERP Software
Mifos – Microfinance Institution management software
Odoo – Open-source ERP, CRM and CMS
Openbravo - Web-based ERP
OrangeHRM – Commercial human resource management
Postbooks – Integrated accounting and ERP business suite
QuickFIX – FIX protocol engine written in C++ with additional C#, Ruby, and Python wrappers
QuickFIX/J – FIX protocol engine written in Java
RCA open-source application
SQL Ledger – Double-entry book-keeping
SugarCRM – Commercial Customer Relationship Management
Tryton - Open-source ERP
TurboCASH – Double-entry book-keeping for Windows
Wave Accounting – Double-entry book-keeping
Integrated Library Management Software
Evergreen – Integrated Library System initially developed for the Georgia Public Library Service's PINES catalog
Koha – SQL-based library management
NewGenLib
OpenBiblio
PMB
refbase – Web-based institutional repository and reference management software
Image editor
Darktable – Digital image workflow management, including RAW photo processing
digiKam – Integrated photography toolkit including editing capabilities
GIMP – Raster graphics editor aimed at image retouching/editing
Inkscape – Vector graphics editor
Krita – Digital painting and sketching application, with a variety of brush engines
LightZone - Free, open-source digital photo editor software application.
RawTherapee – Digital image workflow management aimed at RAW photo processing
Mathematics

Reference management software

Science

Bioinformatics

Cheminformatics
Chemistry Development Kit
JOELib
OpenBabel
Geographic Information Systems

Grid computing
P-GRADE Portal – Grid portal software enabling the creation, execution and monitoring of workflows through high-level Web interfaces
Microscope image processing
CellProfiler – Automatic microscopic analysis, aimed at individuals lacking training in computer vision
Endrov – Java-based plugin architecture designed to analyse complex spatio-temporal image data
FIJI (software) – ImageJ-based image processing
Ilastik – Image-classification and segmentation software
ImageJ – Image processing application developed at the National Institutes of Health
IMOD – 2D and 3D analysis of electron microscopy data
ITK – Development framework used for creation of image segmentation and registration programs
KNIME – Data analytics, reporting, and integration platform
VTK – C++ toolkit for 3D computer graphics, image processing, and visualisation
3DSlicer – Medical image analysis and visualisation
Molecular dynamics
GROMACS – Protein, lipid, and nucleic acid simulation
LAMMPS – Molecular dynamics software
MDynaMix – General-purpose molecular dynamics, simulating mixtures of molecules
NAMD – Parallel efficient simulation of large systems involving millions of atoms
NWChem – Quantum chemical and molecular dynamics software
Molecule viewer
Avogadro – Plugin-extensible molecule visualisation
BALLView – Molecular modeling and visualisation
Jmol – 3D representation of molecules in a variety of formats, for use as a teaching tool
Molekel – Molecule viewing software
MeshLab – Able to import PDB dataset and build up surfaces from them
PyMOL – High-quality representations of small molecules as well as biological macromolecules
QuteMol – Interactive molecule representations offering an array of innovative OpenGL visual effects
RasMol – Visualisation of biological macromolecules
Nanotechnology
Ninithi – Visualise and analyse carbon allotropes, such as Carbon nanotube, Fullerene, Graphene nanoribbons
Plotting

Quantum chemistry

CP2K – Atomistic and molecular simulation of solid-state, liquid, molecular, and biological systems
Risk Management
Active Agenda – Operational risk management and Rapid application development platform
Statistics

Surveys
LimeSurvey – Online survey system
Assistive technology
Speech (synthesis and recognition)
CMU Sphinx – Speech recognition software from Carnegie Mellon University
Emacspeak – Audio desktop
ESpeak – Compact software speech synthesizer for English and other languages
Festival Speech Synthesis System – General multilingual speech synthesis
Modular Audio Recognition Framework – Voice, audio, speech NLP processing
NonVisual Desktop Access – (NVDA) Screen reader, for Windows
Text2Speech – Lightweight, easy-to-use Text-To-Speech (TTS) Software
Other assistive technology
Dasher – Unique text input software
Gnopernicus – AT suite for GNOME 2
Virtual Magnifying Glass - A multi-platform screen magnification tool
Data storage and management
Backup software

Database management systems (including administration)

Data mining
Environment for DeveLoping KDD-Applications Supported by Index-Structures (ELKI) – Data mining software framework written in Java with a focus on clustering and outlier detection methods
Konstanz Information Miner (KNIME)
OpenNN – Open-source neural networks software library written in the C++ programming language
Orange (software) – Data visualization and data mining for novice and experts, through visual programming or Python scripting. Extensions for bioinformatics and text mining
RapidMiner – Data mining software written in Java, fully integrating Weka, featuring 350+ operators for preprocessing, machine learning, visualization, etc. – the previous version is available as open-source
Scriptella ETL – ETL (Extract-Transform-Load) and script execution tool. Supports integration with J2EE and Spring. Provides connectors to CSV, LDAP, XML, JDBC/ODBC, and other data sources
Weka – Data mining software written in Java featuring machine learning operators for classification, regression, and clustering
JasperSoft – Data mining with programmable abstraction layer
Data Visualization Components
ParaView – Plotting and visualization functions developed by Sandia National Laboratory; capable of massively parallel flow visualization utilizing multiple computer processors
VTK – Toolkit for 3D computer graphics, image processing, and visualisation.
Digital Asset Management software system
ResourceSpace – Widely used system with roots in the NGO sector
Disk partitioning software

Enterprise search engines
ApexKB, formerly known as Jumper
Lucene
Nutch
Solr
Xapian
Elasticsearch
ETLs (Extract Transform Load)
Konstanz Information Miner (KNIME)
Pentaho
File archivers

File Systems
OpenAFS – Distributed file system supporting a very wide variety of operating systems
Tahoe-LAFS – Distributed file system/Cloud storage system with integrated privacy and security features
CephFS – Distributed file system included in the Ceph storage platform.
Networking and Internet
Advertising
OpenX
Communication-related
Asterisk – Telephony and VoIP server
Ekiga – Video conferencing application for GNOME and Microsoft Windows
FreePBX – Front-end and advanced PBX configuration for Asterisk
FreeSWITCH – Telephony platform
Jitsi – Java VoIP and Instant Messaging client
QuteCom – Voice, video, and IM client application
Enterprise Communications System sipXecs – SIP Communications Server
Slrn – Newsreader
Twinkle – VoIP softphone
Ring – Cross-platform, peer to peer instant-messaging and video-calling protocol that offers end-to-end encryption and SIP client
Tox – Cross-platform, peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption
E-mail

Geary (software) – Email client based on WebKitGTK+
Mozilla Thunderbird – Email, news, RSS, and chat client
File transfer

Grid and distributed processing
GNU Queue
HTCondor
OpenLava
pexec
Instant messaging

IRC Clients

Middleware
Apache Axis2 – Web service framework (implementations are available in both Java & C)
Apache Geronimo – Application server
Bonita Open Solution – a J2EE web application and java BPMN2 compliant engine
GlassFish – Application server
Jakarta Tomcat – Servlet container and standalone webserver
JBoss Application Server – Application server
ObjectWeb JOnAS – Java Open Application Server, a J2EE application server
TAO (software) – C++ implementation of the OMG's CORBA standard
Enduro/X – C/C++ middleware platform based on X/Open group's XATMI and XA standards
RSS/Atom readers/aggregators
Akregator – Platforms running KDE
Liferea – Platforms running GNOME
RSS Bandit – Windows, using .NET Framework
RSSOwl – Windows, Mac OS X, Solaris, Linux using Java SWT Eclipse
Sage (Mozilla Firefox extension)
Peer-to-peer file sharing


Popcorn Time – Multi-platform, free, and open-source media player
qBittorrent – Alternative to popular clients such as μTorrent
Portal Server
Drupal
Liferay
Oxwall – Community site software
Sun Java System Portal Server
uPortal
Remote access and management
FreeNX
OpenVPN
rdesktop
Synergy
VNC (RealVNC, TightVNC, UltraVNC)
Remmina
Routing software

Web browsers

Brave – Free and open-source web browser based on the Blink engine
Chromium – Minimalist web browser from which Google Chrome draws its source code
Firefox – Mozilla-developed web browser using the Gecko layout engine
Midori – Lightweight web browser using the WebKit layout engine
Tor Browser – Modified Mozilla Firefox ESR web browser
Waterfox – Alternative to Firefox (64-bit only)
SeaMonkey – Free and open-source Internet suite
Webcam
Cheese – GNOME webcam application
Guvcview – Linux webcam application
Webgrabber
cURL
HTTrack
Wget
Web-related
Apache Cocoon – A web application framework
Apache – The most popular web server
AWStats – Log file parser and analyzer
BookmarkSync – Tool for browsers
Cherokee – Fast, feature-rich HTTP server
curl-loader – Powerful HTTP/HTTPS/FTP/FTPS loading and testing tool
FileZilla - FTP
Hiawatha – Secure, high performance, and easy-to-configure HTTP server
HTTP File Server – User-friendly file server software, with a drag-and-drop interface
lighttpd – Resource-sparing, but also fast and full-featured, HTTP Server
Lucee – CFML application server
Nginx – Lightweight, high performance web server/reverse proxy and e-mail (IMAP/POP3) proxy
NetKernel – Internet application server
Qcodo – PHP5 framework
Squid (software) – Web proxy cache
Vaadin – Fast, Java-based framework for creating web applications
Varnish (software) – High-performance web application accelerator/reverse proxy and load balancer/HTTP router
XAMPP – Package of web applications including Apache and MariaDB
Zope – Web application server
Other networking programs
JXplorer – LDAP client
Nextcloud – A fork of ownCloud
OpenLDAP – LDAP server
ownCloud – File share and sync server
Wireshark – Network monitor
YaCy – P2P-based search engine
Educational
Educational suites
ATutor – Web-based Learning Content Management System (LCMS)
Chamilo – Web-based e-learning and content management system
Claroline – Collaborative Learning Management System
DoceboLMS – SAAS/cloud platform for learning
eFront – Icon-based learning management system
FlightPath – Academic advising software for universities
GCompris – Educational entertainment, aimed at children aged 2–10
Gnaural – Brainwave entrainment software
H5P – Framework for creating and sharing interactive HTML5 content
IUP Portfolio – Educational platform for Swedish schools
ILIAS – Web-based learning management system (LMS)
Moodle – Free and open-source learning management system
OLAT – Web-based Learning Content Management System
Omeka – Content management system for online digital collections
openSIS – Web-based Student Information and School Management system
Sakai Project – Web-based learning management system
SWAD – Web-based learning management system
Tux Paint – Painting application for 3–12 year olds
UberStudent – Linux based operating system and software suite for academic studies
Geography
KGeography – Educational game teaching geography
Learning support

Language
Kiten
KVerbos
Typing
KTouch – Touch typing lessons with a variety of keyboard layouts
Tux Typing – Typing tutor for children, featuring two games to improve typing speed
File managers

Games

Application layer
WINE – Allows Windows applications to be run on Unix-like operating systems
Genealogy

Graphical user interface
Desktop environments

Window managers

Windowing system

Groupware

Content management systems

Wiki software

Healthcare software

Hobby software
Homebrewing
CyberBrau
Media
2D animation
Pencil2D – Simple 2D graphics and animation program
Pivot Animator – Application used to create stick figure and sprite animations
Synfig – 2D vector graphics and timeline based animation
TupiTube (formerly KTooN) – Application for the design and creation of animation
OpenToonz – Part of a family of 2D animation software
3D animation
Blender – Professional computer graphics software featuring modeling, sculpting, texturing, rigging, simulation, rendering, camera tracking, video editing, and compositing
OpenFX – Modeling and animation software with a variety of built-in post processing effects
Seamless3d – Node-driven 3D modeling software
Audio editors, audio management

CD/USB-writing software

Flash animation
Pencil2D – For animations
SWFTools – For scripting
Graphics

Image galleries

Image viewers
Eye of GNOME
F-spot
Geeqie
Gthumb
Gwenview
Kphotoalbum
Opticks
Multimedia codecs, containers, splitters

Television



Video converters

Dr. DivX
FFmpeg
MEncoder
OggConvert
Video editing

Avidemux
AviSynth
Blender
Cinelerra
DScaler
DVD Flick
Flowblade
Kaltura
Kdenlive
Kino
LiVES
Natron
OpenShot Video Editor
Pitivi
Shotcut
VirtualDub
VirtualDubMod
VideoLAN Movie Creator
Video encoders

Avidemux
HandBrake
FFmpeg
Video players

Media Player Classic
VLC media player
Other media packages
Celtx – Media pre-production software
Office suites
Apache OpenOffice (formerly known as OpenOffice.org)
Calligra Suite– The continuation of KOffice under a new name
LibreOffice– Independent Work of OpenOffice.org with a number of enhancements
ONLYOFFICE Desktop Editors– An open-source offline edition of the Cloud
Operating systems
Be advised that available distributions of these systems can contain, or offer to build and install, added software that is neither free software nor open-source.

Emulation and Virtualisation


VirtualBox
Personal information managers
Chandler – Developed by the OSAF
KAddressBook
Kontact
KOrganizer
Mozilla Calendar – Mozilla-based, multi-platform calendar program
Novell Evolution
OpenSync (software)
Project.net – Commercial Project Management
TeamLab – Platform for project management and collaboration
Programming language support

Bug trackers
Bugzilla
Mantis
Mindquarry
Redmine
Trac
Code generators
Bison
CodeSynthesis XSD – XML Data Binding compiler for C++
CodeSynthesis XSD/e – Validating XML parser/serializer and C++ XML Data Binding generator for mobile and embedded systems
Flex lexical analyser – Generates lexical analyzers
Kodos
Open Scene Graph – 3D graphics application programming interface
OpenSCDP – Open Smart Card Development Platform
phpCodeGenie
SableCC – Parser generator for Java and .NET
SWIG – Simplified Wrapper and Interface Generator for several languages
^txt2regex$
xmlbeansxx – XML Data Binding code generator for C++
YAKINDU Statechart Tools – Statechart code generator for C++ and Java
Documentation generators
Doxygen – Tool for writing software reference documentation. The documentation is written within code.
Mkd – The software documentation is extracted from the sources files, from pseudocode or comments.
Natural Docs – Claims to use a more natural language as input from the comments, hence its name.
Configuration software
Autoconf
Automake
BuildAMation
CMake
Debuggers (for testing and trouble-shooting)
GNU Debugger – A portable debugger that runs on many Unix-like systems
Memtest86 – Stress-tests RAM on x86 machines
Xnee – Record and replay tests
Integrated development environments

Version control systems

Screensavers
BOINC
Electric Sheep
XScreenSaver
Security
Antivirus
ClamAV
ClamWin
Gateway Anti-Virus
Lynis
Data loss prevention
MyDLP
Data recovery
dvdisaster
Foremost
PhotoRec
TestDisk

Forensics
The Coroner's Toolkit
The Sleuth Kit
Anti-forensics
USBKill
Disk erasing
DBAN
srm
Encryption
AES
GnuPG
GnuTLS
KGPG
NaCl
OpenSSL
Seahorse
Signal
TextSecure
wolfCrypt
Disk encryption
CrossCrypt
FreeOTFE and FreeOTFE Explorer
eCryptfs
Database encryption
Mydiamo
Firewall
Coyote Linux
Firestarter
IPFilter
ipfw
iptables
M0n0wall
PeerGuardian
PF
pfSense
Rope
Shorewall
SmoothWall
Untangle
Vyatta
Network and security monitoring

Secure Shell (SSH)
Cyberduck – Mac OS X and Windows client (since version 4.0)
Lsh – Server and client, with support for SRP and Kerberos authentication
OpenSSH – Client and server
PuTTY – Client-only
Password management
KeePass
Password Safe
Mitro
Other security programs

Theology
Bible study tools
Go Bible – A free Bible viewer application for Java mobile phones
Marcion – Coptic–English/Czech dictionary
OpenLP – A worship presentation program licensed under the GNU General Public License
The SWORD Project – The CrossWire Bible Society's free software project
Typesetting

See also

Comparison of file synchronization software §Open-source
List of HDL simulators §Free and open-source simulators
List of optimization software §Free and open-source software
List of concept- and mind-mapping software §Free and open-source
List of spreadsheet software §Free and open-source software
Comparison of FTP client software §Free and open-source software
GNOME Core Applications
List of GNU packages
List of KDE applications
List of formerly proprietary software
List of Unix commands
General directories
AlternativeTo
CodePlex
Free Software Directory
Freecode
Open Hub
SourceForge



, a collection of FOSS organized by target audience.
, a community-driven archive of open-source software (OSS).
, a pre-assembled ISO image of OSS for Windows
, maintained by the Ubuntu Documentation Project.
, a list of free and open-source software for Windows