• 1996: Richard Lee and Adam Feder created the proprietary in-house tool, CosmoSynergy.
• 1998: CosmoSynergy was developed in-house at Cosmo Software with Chris Schoeneman's help.
• 2000: SGI decided to close down Cosmo Software and never productized CosmoSynergy.
• 2001: Chris Schoeneman began writing Synergy from scratch with Linux support.
• 2002: Synergy was first released under GPL v2 and Windows support was added.
• 2003: macOS support was added, allowing sharing between all three major platforms.
• 2006: Development slowed as Chris had to prioritize other aspects of his life.
• 2008: A new fork, Synergy+ was created by Sorin Sbârnea on Google Code.
• 2009: Nick Bolton began contributing and later took responsibility for leading the project.
• 2010: Donations were accepted to help fund the project which was used to hire developers.
• 2011: Synergy+ was renamed back to Synergy and QSynergy by Volker Lanz was added as the GUI.
• 2012: Symless was formed as an employer for the developers who continued to add improvements.
• 2016: Wayland development began but struggled to progress due to security limitations in Wayland.
• 2017: Synergy 2 was launched as a more user-friendly proprietary tool for less technical users.
• 2018: Due to stability issues, Synergy 2 was rolled back to beta, and the Barrier fork was created.
• 2021: Barrier was forked to Input Leap, giving project maintainers more freedom over changes.
• 2022: Wayland development restarted on the Barrier fork and later moved to Input Leap and Synergy.
• 2023: Synergy 3 was officially launched by Symless, which uses Synergy 1 as its open core.
• 2024: The Deskflow project was created as the community-driven upstream of Synergy.

Written in early 2000s by Chris Schoeneman:

The first incarnation of synergy was CosmoSynergy, created by Richard Lee and Adam Feder then at Cosmo Software, Inc., a subsidiary of SGI (nee 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.