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Synergy (software)
Synergy (software)
Synergy (software)
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Synergy
Original authorChris Schoeneman
DeveloperSymless
Initial release13 May 2001; 24 years ago (2001-05-13)[1]
Stable release
1.20.0[2] Edit this on Wikidata / 5 November 2025; 3 months ago (5 November 2025)
Written inC++
Operating systemCross-platform
LicenseProprietary and GPLv2[3]
Websitesymless.com/synergy
Repository

Synergy is a software application for sharing a keyboard and mouse between multiple computers. It is used in situations where several PCs are used together, with a monitor connected to each, but are to be controlled by one user. The user needs only one keyboard and mouse on the desk—similar to a KVM switch without the video.

Partly open source and partly closed source, the open source components are released under the terms of the GNU General Public License, which is free software. The first version of Synergy was created on May 13, 2001, by Chris Schoeneman and worked with the X Window System only. Synergy now supports Windows, macOS, Linux, and other Unix-like operating systems.

Design

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Once the program is installed, users can move the mouse "off" the side of their desktop on one computer, and the mouse pointer will appear on the desktop of another computer. Key presses will be delivered to whichever computer the mouse-pointer is located in. This makes it possible to control several machines as easily as if they were a single multi-monitor computer. The clipboard and even screensavers can be synchronized.

The program is implemented as a server which defines which screen-edges lead to which machines, and one or more clients, which connect to the server to offer the use of their desktops. The keyboard and mouse are connected to the server machine.

As of version 2.0 (2017) keystrokes, mouse movements, and clipboard contents are sent via an encrypted SSL network connection. This previously required the purchase of the Pro edition in version 1. In July 2013, the Defuse Security Group reported[4] the proprietary encryption used in Synergy 1.6 to be insecure and released an exploit that could be used to passively decrypt the commands sent to the Synergy 1.6 clients.[5] This was solved by using SSL in 1.7.

TCP/IP communications (default port 24800[6]) are used to send mouse, keyboard, and clipboard events between computers in Synergy 1.

History

[edit]

The first incarnation of Synergy was CosmoSynergy, created by Richard Lee and Adam Feder then at Cosmo Software, Inc., a subsidiary of SGI (née Silicon Graphics, Inc.), at the end of 1996. They wrote it, and Chris Schoeneman contributed, to solve a problem: most of the engineers in Cosmo Software had both an Irix and a Windows box on their desks, and switchboxes were expensive and annoying. CosmoSynergy was a great success, but Cosmo Software declined to productize it, and the company was later closed. Synergy is a from-scratch reimplementation of CosmoSynergy. It provides most of the features of the original and adds a few improvements.

Synergy+ was created in 2009 as a maintenance fork for the purpose of fixing bugs inherited from the original version. The original version of Synergy had not been updated for a notable length of time (as of 6 June 2010, the latest release was 2 April 2006).[7] There was never official confirmation that the original Synergy project had been abandoned; however, there was public discussion providing speculation.[8] In said discussion, Chris Schoeneman (the creator of Synergy)[9] stated that instead of supporting a 1.3.x team, he intends on releasing version 2.0 of Synergy, and publicly announced on 27 Aug 2008 that he has been making progress on this version.[10]

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Synergy (software)

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from Grokipedia
Synergy is a application that allows users to control multiple computers using a single , keyboard, and over a local network, eliminating the need for separate input devices on each machine. Developed by Symless, it supports Windows, macOS, and operating systems, enabling seamless interaction between heterogeneous setups such as a Windows primary computer controlling macOS and secondary machines. The software operates in a client-server model, where one computer acts as the server sharing its peripherals, while others function as clients receiving input, with features like automatic screen layout configuration and secure TLS/SSL encryption ensuring reliable and protected communication. Originally created in 2001 by Chris Schoeneman as an open-source project, was later forked and actively developed starting in 2007 by , who founded Symless to sustain its growth through commercial licensing. Early versions, including 1, were built on a model before transitioning to paid licenses to fund a dedicated development team, with 2 introducing a graphical configuration interface in 2014. As of October 2025, the latest release is 3 version 3.4.0, which features a modern , auto-discovery of devices, and improved performance, including ARM64 support for broader hardware compatibility. Synergy's core engine is based on the open-source Deskflow project, which Symless maintains as the upstream repository, contributing code, financial resources, and bug fixes to ensure community-driven advancements. While Deskflow provides a free, GPL-licensed alternative for users willing to compile from source, Synergy offers a polished, ready-to-use commercial version with enhanced support, regular updates, and enterprise-grade stability; according to Symless, it is adopted by 26% of companies including , Amazon, and Apple. This dual model has fostered related open-source forks like Barrier and Input Leap, expanding accessibility while Symless focuses on premium features such as and hotkey customization.

Overview

Purpose and Core Functionality

Synergy is a software application designed to share a single keyboard and across multiple networked computers, allowing users to control them seamlessly from one without the need for physical hardware switches. It functions similarly to a software-based KVM (keyboard, video, ) switch, but excludes video signal transmission, focusing instead on emulation over a local network. This enables efficient management of multi-computer environments, particularly in productivity-focused setups where users operate several machines simultaneously. The primary use cases for include multi-computer workstations common among developers who need to switch between different operating systems, such as testing code across Windows, macOS, and environments, as well as office settings with multiple monitors distributed across separate machines for tasks like or . Key benefits for users include the elimination of cumbersome physical device switching, support for an unlimited number of connected computers, and enhanced workflow efficiency in cross-platform scenarios. Notably, is utilized by 26% of companies, including , Amazon, Apple, , , , GE, and HP, to streamline complex input sharing in their operations. In its basic workflow, Synergy arranges the connected computers in a virtual layout mimicking their physical screen positions; the cursor moves fluidly from one screen to another by crossing defined edges, automatically shifting control to the target computer, while keyboard input follows the currently active screen. As a supplementary feature, it also supports sharing for text and images between machines, further integrating the across devices.

Supported Platforms and Requirements

Synergy supports a range of desktop operating systems, enabling cross-platform use across Windows, macOS, and environments. Specifically, it is compatible with and Windows 11. On macOS, supported versions include macOS 15 Sequoia and macOS 26 Tahoe, with a minimum requirement of macOS 12 Monterey or higher. For , Synergy works on various distributions such as 24.04 LTS and 24.10 (x86_64), as well as 40 or higher, with broader compatibility across Debian-based, RPM-based, and other major distributions like and openSUSE, provided they include recent libraries. Additionally, Synergy supports Wayland on , enhancing compatibility with modern display servers. Unix-like systems, including BSD variants such as , are supported through source compilation, though official binaries focus on major desktop platforms. Hardware requirements for are minimal, as the software is designed to run efficiently on standard modern personal computers equipped with network connectivity via Ethernet or . No specific CPU speed or RAM thresholds are mandated beyond those implied by the supported operating systems, allowing it to operate on a wide array of hardware configurations without significant resource demands. All connected computers must be on the same local network to facilitate seamless input sharing. Installation is straightforward, with platform-specific installers available for download from the official Symless website, supporting easy deployment on Windows, macOS, and popular distributions. For less common systems, users can build from source following the provided guidelines. However, Synergy does not support mobile operating systems such as , Android, or , limiting its use to desktop and server environments.

Technical Design

Server-Client Architecture

Synergy employs a client-server architecture where a single server computer, connected to the physical keyboard and , acts as the central hub for input sharing, while one or more client computers receive and apply these inputs to control their respective screens. The server maintains awareness of the overall layout of connected screens and directs input events—such as movements, clicks, keystrokes, data, and screen saver activations—to the appropriate client based on the cursor's position. This model allows users to seamlessly transition between computers as if operating a single extended desktop, with the server processing local inputs normally while relaying them over to clients. Configuration in Synergy is managed through a text-based configuration file that defines the spatial arrangement of screens, enabling flexible setups for multiple monitors. The file uses structured sections such as "screens" to name and customize individual computers (e.g., assigning half-duplex behavior or meta key mappings like Alt), "aliases" for hostname variations, and "links" to specify relative positions like "right = client2" or partial overlaps with percentage ranges (e.g., "up(50,100) = client3(0,50)"). Absolute positioning can be approximated through these relative directives or range specifications, while global "options" set parameters like protocol selection or delays. Hotkeys, defined within the configuration or via graphical interfaces, facilitate manual screen switching, such as using to lock the cursor to a specific client for focused control. Input handling relies on the server detecting when the mouse cursor approaches or crosses screen edges in the defined layout, triggering a switch to the adjacent client and relaying events accordingly. Mouse movements are typically sent in absolute mode for precise positioning across screens, but a relative mouse mode option—enabled via the configuration (e.g., "relativeMouseMoves = true")—allows for relative movements when the cursor is locked to a client, which is useful for applications like gaming that require smooth, unaccelerated input. All communication occurs over TCP/IP on the default port 24800, ensuring reliable event transmission between the server and clients. Communications are encrypted to secure the data in transit. The architecture supports for setups with two or more computers, accommodating grid-like arrangements or custom layouts without inherent limits on the number of clients, though practical performance depends on network conditions and hardware. This design prioritizes low-latency interaction across diverse operating systems, making it suitable for multi-computer workstations.

Network and Mechanisms

Synergy employs a TCP/IP-based protocol for streaming input events, such as mouse movements and keystrokes, between computers in a server-client configuration. The primary communication occurs over TCP port 24800, which handles both control signals and data transmission. In Synergy 3, additional TCP ports 24802 and 24804 support background services for configuration and auto-discovery of devices on the local network, simplifying setup without manual IP configuration. Early versions of Synergy, particularly 1.6, relied on a custom, proprietary encryption scheme that proved vulnerable to passive decryption attacks due to its use of a weak block cipher implementation without proper authentication or sequencing. In July 2013, security researchers at Defuse Security publicly disclosed this flaw and demonstrated an exploit that allowed interception and manipulation of transmitted data, prompting immediate upgrades. Starting with version 1.7 in 2015, Synergy transitioned to optional SSL/TLS encryption powered by the OpenSSL library, enabling secure connections to mitigate man-in-the-middle risks. Synergy 2, released in 2017, integrated SSL as a core Pro edition feature for enhanced protection, while the open-source fork Barrier maintained compatibility with these improvements. In Synergy 3, TLS encryption is supported with modern protocol versions using OpenSSL. To ensure reliable operation, users must configure firewall rules to permit inbound and outbound traffic on 24800 (and additional ports in Synergy 3), as blocking these can prevent connections. Newer versions incorporate UDP-based auto-discovery mechanisms within the background service to detect servers and clients on the same LAN, reducing setup complexity while maintaining compatibility with standard firewall configurations. Without encryption enabled, Synergy traffic is susceptible to eavesdropping or injection attacks on unsecured networks, particularly from rogue servers impersonating legitimate ones. For remote or internet-based use, official guidance and community recommendations strongly advise tunneling Synergy over a VPN to encrypt the entire connection and avoid exposing sensitive input data.

Development History

Origins and Initial Releases

The origins of Synergy trace back to 1996, when Richard Lee and Adam Feder developed CosmoSynergy as a proprietary in-house tool at Cosmo Software, a of Inc. (SGI). This precursor software was designed to enable keyboard and mouse sharing between Unix workstations running and Windows systems, addressing the limitations of hardware KVM switchboxes for teams. Schoeneman contributed to CosmoSynergy's development during his time at Cosmo Software in 1998, but the project was never commercialized as an external product. Following the closure of Cosmo Software in 1998, in 2001 Schoeneman initiated a from-scratch reimplementation of the concept, naming it Synergy and focusing initially on Linux support through the X Window System. The software was released as open-source under the GNU General Public License version 2 (GPLv2) in 2002, providing basic functionality for sharing a mouse and keyboard across multiple computers on a network. At this stage, Synergy targeted Linux and Unix environments, with Windows support added in the initial release to enable cross-platform use within local networks. Early versions faced challenges inherent to their foundational design, including restriction to local area networks (LANs) due to reliance on direct TCP/IP connections without advanced remote access features. Support for macOS was absent until 2003, limiting broader adoption beyond Unix-based systems and early Windows integration. These constraints reflected Synergy's origins as a lightweight, open-source solution for desktop productivity rather than a comprehensive remote control tool.

Major Evolutions and Forks

Following the initial releases, development of the original project stagnated after its last significant update in April 2006, as creator Chris Schoeneman shifted focus to other priorities. In 2008, Schoeneman announced plans to work on version 2.0, but progress was delayed, leading to a lack of updates for several years. To address persistent bugs and the project's inactivity, the community initiated the fork in 2008, led by Sorin Sbârnea on Code, with the primary goal of maintenance and bug fixes inherited from the original codebase. Contributions from in 2009 accelerated development, and by 2011, was renamed back to Synergy, incorporating enhancements like the graphical user interface developed by Volker Lanz. This fork evolved into multiple variants, including efforts to improve cross-platform compatibility and add features such as Wayland support starting in 2016, though security limitations hindered full implementation at the time. In a commercial shift, Symless—founded in 2012 by —took over Synergy's development to fund ongoing improvements through donations and later professional hires. Symless released Synergy 2 in beta in July 2017 and as a stable version in November 2017, introducing a model with significant enhancements for easier configuration and setup across Windows, macOS, and . However, stability issues prompted a rollback to beta status in 2018. Community dissatisfaction with the proprietary direction led to further forks of the open-source Synergy 1.x branch. In 2018, Barrier emerged as an open-source fork of Synergy 1.9, aiming to maintain free access and address unresolved issues like clipboard synchronization and modifier key handling. By 2025, Barrier had become abandoned, with its GitHub repository stagnant, unreviewed pull requests, and no active maintainer engagement due to internal disputes and technical debt. In response, Input Leap forked from Barrier 2.4 in 2021, providing a more active community-driven alternative with emphasis on Linux enhancements, including renewed Wayland development efforts in 2022 to improve compatibility with modern desktop environments. More recently, Symless began sponsoring the open-source core, contributing code and financial support to consolidate efforts and reduce fragmentation. This culminated in the 2024 launch of the Deskflow project as the new upstream for Synergy 1.x, Input Leap, and Barrier, effectively renaming and revitalizing the Synergy Community Edition with integrated contributions from prior forks. Deskflow serves as a testing ground for features like improved encryption protocols, benefiting both community users and Symless's commercial 3 release from 2023.

Licensing and Availability

Open Source Elements

The core engine of Synergy has been released under the GNU General Public License version 2 (GPLv2) since its initial development in 2001. This licensing allows users to freely access, modify, and distribute the source code, fostering an ecosystem for the software's foundational components. The source code for the core engine is hosted on in two primary repositories: symless/synergy, which maintains the codebase for 1 and the core elements of 3, and deskflow/deskflow, the upstream community project. In 2024, the Deskflow project emerged as a dedicated open-source initiative sponsored by Symless, the company behind the commercial Synergy product, to serve as the free, community-maintained backend for keyboard and mouse sharing functionality. Deskflow is licensed under the GNU General Public License version 2.0 (GPLv2) with an exception. Deskflow focuses on prototyping and iterating core features through collaborative development, with Symless providing financial support and code contributions to ensure sustainability. As of November 2025, its latest release is version 1.24.0 (pre-release), dated November 17, 2025, including bug fixes and improvements to core stability, available for download via and package managers. Community contributions to the open-source elements occur primarily through the deskflow/deskflow repository, where developers submit issues and pull requests to enhance core functionality such as network protocols and input handling, excluding graphical user interfaces. This model encourages broad participation while keeping development centered on essential, non-commercial aspects of the software. While the open-source components provide a robust foundation, accessing full features like advanced configuration tools and official requires a commercial from Symless, as the version lacks enterprise-level assistance. Forks such as Input Leap have derived from this open-source base to extend compatibility and features independently.

Commercial Versions and Symless

Symless, founded in 2008 and incorporated in 2012 in the United Kingdom, serves as the primary maintainer and commercial provider of Synergy, transforming the open-source project into a supported enterprise solution for multi-computer input sharing. The company, led by CEO , focuses on developing proprietary enhancements, ensuring security, and offering paid licenses to users seeking reliable, professional-grade functionality across Windows, macOS, and platforms. Originally created by Chris Schoeneman in , Synergy's codebase has been stewarded by Symless since its formation, with the firm monetizing advanced features while sponsoring the upstream Deskflow community project through code contributions and financial support. The commercial evolution of Synergy includes distinct version lineages tailored for stability and modern needs. Synergy 1 represents the mature, battle-tested iteration, with its latest release, version 1.18.1, issued on August 18, 2025, emphasizing core reliability for enterprise environments without major interface overhauls. Introduced in 2017, Synergy 2 marked a shift toward simplified setup and mandatory SSL/TLS for secure connections, though it was discontinued in favor of upgrades to later . Synergy 3, launched in 2023 with its beta debut on March 21, builds on this foundation through a complete GUI rebuild for intuitive configuration, automatic device discovery and setup, and experimental Wayland support on starting in version 3.2.1 released November 25, 2024; the most recent update, version 3.4.0 on October 22, 2025, incorporates core enhancements from version 1.19. Licensing for commercial Synergy adopts a one-time purchase model for personal and small-scale use, starting at approximately $29 for the basic Synergy 3 edition, which supports up to three computers with features like cross-platform copy-paste and basic technical support. Higher tiers, such as Synergy 3 Ultimate at $49, extend capabilities for advanced personal setups, while business and enterprise options scale to larger deployments—up to 50 users for around $332 annually or perpetual licenses with multi-year support starting at $376—catering to organizational needs with priority assistance and unlimited screens. A free trial is available, offering 14 days for personal users and 28 days for business evaluations, allowing testing without upfront commitment. In 2025, Symless advanced Synergy's infrastructure with planned integrations like Go-based services for improved performance and a potential Go-implemented GUI, alongside major core upgrades to address evolving demands such as enhanced Wayland compatibility and post-2020 platform shifts, ensuring continued relevance in hybrid work environments. These developments fill gaps in legacy support, focusing on seamless and cross-OS for professional users.

References

  1. https://symless.com/synergy
  2. https://symless.com/synergy/news/my-cpp-journey
  3. https://symless.com/synergy/news/the-synergy-story-so-far
  4. https://symless.com/synergy/download/release-notes/36
  5. https://symless.com/synergy/open-source
  6. https://github.com/deskflow/deskflow
  7. https://symless.com/synergy/news/why-did-barrier-fail
  8. https://symless.com/synergy/features
  9. https://help.symless.com/hc/en-us/articles/33562793892497-Operating-system-and-hardware-requirements
  10. https://github.com/symless/synergy-odin
  11. https://symless.com/synergy/news/synergy-3-is-gaining-traction
  12. https://help.symless.com/hc/en-us/articles/33739042001553-Start-here-Install-and-configure
  13. https://help.symless.com/hc/en-us/articles/33564018470929-Does-Synergy-work-with-iOS-Android-or-ChromeOS
  14. https://github.com/deskflow/deskflow/wiki/How-it-works
  15. https://github.com/deskflow/deskflow/wiki/Server-Text-Config
  16. https://github.com/deskflow/deskflow/wiki/Command-Line
  17. https://help.symless.com/hc/en-us/articles/35716657396113-What-ports-does-Synergy-use
  18. https://help.symless.com/hc/en-us/articles/33842760143761-Synergy-Business-Common-Questions-Security-Compliance
  19. https://defuse.ca/cracking-synergy-bad-cryptography.htm
  20. https://forums.symless.com/topic/344-synergy-173-released/
  21. https://www.n00py.io/2017/03/compromising-synergy-clients-with-a-rogue-synergy-server/
  22. https://forums.symless.com/topic/1926-how-to-use-synergy-between-local-lan-and-vpn-connected-pcs/
  23. https://symless.com/synergy/about
  24. https://github.com/deskflow/deskflow/wiki/History
  25. https://www.cnet.com/tech/tech-industry/sgi-to-shutter-cosmo-software/
  26. https://forums.symless.com/topic/5371-synergy-2-unofficial-edition-2-documentation/
  27. https://github.com/deskflow/deskflow/wiki/Project-Forks
  28. https://github.com/symless/synergy
  29. https://github.com/deskflow/deskflow/blob/master/LICENSE
  30. https://github.com/deskflow/deskflow/wiki/Relationship-with-Synergy
  31. https://sourceforge.net/projects/deskflow.mirror/
  32. https://github.com/deskflow/deskflow/releases
  33. https://github.com/deskflow/deskflow/wiki/Contributing
  34. https://github.com/input-leap/input-leap/wiki/History
  35. https://tracxn.com/d/legal-entities/united-kingdom/symless-limited/__iYuIj858s-0oz1802bdkCScqYO5hzKdt0Og8PddF4aY
  36. https://symless.com/synergy/download/release-notes/30
  37. https://help.symless.com/hc/en-us/articles/33562819211025-What-is-the-difference-between-each-version-of-Synergy
  38. https://symless.com/synergy/news/synergy-3-beta-launch
  39. https://symless.com/synergy/download/release-notes/11
  40. https://symless.com/synergy/purchase
  41. https://www.insight.com/en_US/shop/product/SB36-US32/symless/SB36/Symless-Synergy-Business-Subscription-license-3-years-Up-to-50-users/
  42. https://www.insight.com/en_US/shop/product/SYMSYNPERPLICWSUP/symless/SYM-SYN-PERP-LIC-WSUP/Symless-Synergy-Business-Perpetual-License-36-Months-of-Support/
  43. https://help.symless.com/hc/en-us/articles/360007047777-Do-you-offer-a-free-trial
  44. https://symless.com/synergy/roadmap
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