The Project

Ciao is an open source project developed by the Ciao team and many contributors. The core Ciao system is provided under the GNU LGPL license.

The code is available as Git repositories both at:


Ciao is an open source project. We welcome contributions in any form:

  • links to third-party code using Ciao,
  • report of bugs (both correctness and efficiency) and mistakes in the documentation,
  • request of improvements and new features (compliance with standards, new libraries, support for specific operating system or platforms, installers, etc.),
  • source code patches.
Preferably, use the the following moderated mailing lists (they reach the Ciao developers only):

Additionally, you can also fill github issues at our public repository mirror or gitlab issues (intented mainly for internal use; requires login).

The Team

Ciao is in very active and continuous development since the early 90's by an international team, coordinated by CLIP group members at UPM and the IMDEA Software Institute.

Ciao builds on its predecessor, &-Prolog, developed between 1984 and the mid 90's at the University of Texas at Austin, USA, the Microelectronics and Technology Corporation, and UPM. Past versions of Ciao are available at the legacy archive.