OnlyWorlds is an open standard for worldbuilding. It defines how 22 element categories (characters, locations, creatures, etc.) are structured and related within fictional or historical settings.

Worlds following this specification are stored as structured text files. Any application using the OnlyWorlds standard can read, edit, and transfer these files. The specification is open source with no licensing restrictions.

OnlyWorlds includes essentials tools, developer resources, and a growing ecosystem of compatible software. Worlds can be stored and used with no restrictions, and OnlyWorlds offers free world hosting and transfer services.

Infrastructure

Core language
YAML schema defining 22 element categories, their fields, and relationships
Web platform
Free account creation, world management, and element storage at onlyworlds.com
World API
REST API for applications to access and exchange world data
Compatible tools
Software for creating, mapping, writing, and visualizing OnlyWorlds-format worlds
World migration
Free AI-powered tools to convert existing worldbuilding content into OnlyWorlds format
Developer resources
Packages, guides, AI support and a foundational tool so anyone can build or integrate personal tools and commercial applications
Community channels
Organized feedback systems, feature requests, and collaborative improvement

Documentation

Getting Started
Introduction to OnlyWorlds concepts and guides for creating and migrating worlds
Specification
Complete technical reference for worlds, elements, fields, relationships, and advanced concepts
Tool Directory
Available software for creating, editing, and managing OnlyWorlds data
Contribution
Systems and guidelines for contributing to the OnlyWorlds specification and ecosystem
Developer Support
Technical documentation and resources for developing OnlyWorlds applications
Vision & History
Project philosophy, goals, and evolution
create a world • join Discord • view on GitHub

⚠️ Pre-Launch Status: OnlyWorlds launches September 2025. Core functionality is complete and available for early adopters.