Retro is a modern, pragmatic Forth drawing influence from many sources. It is clean, elegant, tiny, easy to grasp, and adaptable to many tasks.

It's not a traditional Forth. Drawing influence from colorForth, it uses prefixes to guide the compiler. From Joy and Factor, it uses quotations (anonymous, nestable functions) and combinators (functions that operate on functions) for much of the stack and flow control. It also adds vocabularies for working with strings, arrays, and other data types. Source files are written in Unu, allowing for simple, literate sources.

The source and documentation are distributed under the ISC license.


RetroForth 2023.9 (source, documentation, and examples)


Updated from the development snapshots.

Latest Documentation (epub)

Latest Documentation (text)

Glossary (text)

Glossary [concise] (text)

Additional Documents


Latest Snapshot

retro.c (amalgamation, for BSD, Linux, macOS, Haiku, and Windows)





#retro on (Matrix)

IRC Logs

Bug Reports

Development is supported by a wonderful set of patrons over on patreon.

Thanks to Kiyoshi Yoneda, Krinkleneck, Rick Carlino, Scott McCallum, Bartels Jon Randy, Nuno, Eli, Brad S, Tobias Ammann, oneearedrabbit, Octavio Turra, and Dave S for their support.

If you are interested in a related, but smaller system, take a look at Konilo.