OnlyWorlds is an open data language for worldbuilding. It defines 22 element categories with structured fields and relationships, for worlds that are portable across tools and computationally usable.
The platform facilitates worldbuilding through hosting, tooling, and an open language. Core services and essential tools remain free, and worlds belong to their creators: portable, offline, always yours.
Try the ecosystem explorer for an interactive introduction (best on desktop). See getting started to jump right in as world builder or developer.
Infrastructure
Language
YAML schema defining element categories, fields, and relations
Web Platform
World creation and management
World API
REST APIs for world exchange
Tool Directory
A growing list of free tools
Development Support
Repos, packages, APIS, AI support