Rebol ( ; historically REBOL) is a cross-platform data exchange language and a multi-paradigm dynamic programming language designed by Carl Sassenrath for network communications and distributed computing. It introduces the concept of dialecting: small, optimized, domain-specific languages for code and data, which is also the most notable property of the language according to its designer Carl Sassenrath:
Originally, the language and its official implementation were proprietary and closed source, developed by REBOL Technologies. Following the discussion with Lawrence Rosen, the Rebol version 3 interpreter was released under the Apache 2.0 license on December 12, 2012. Older versions are only available in binary form, and no source release for them is planned.