SessionZero is built to be a flexible, minimal companion for any tabletop RPG system you want to run, from popular games to niche homebrew. It's designed to get out of your way and put you in total control of your game data.
We believe your data should always be yours. That's why SessionZero is built around three core principles: it's system-agnostic, offline-first, and truly open source (AGPL-3.0).
The Core of SessionZero
System-Agnostic Datapacks
The entire application is driven by Datapacks (.szp files). These are structured archives of JSON files and assets that define a game system's rules, character sheets (Templates), and content (Datasets like items and monsters). If you can define it, you can play it.
Offline-First & Self-Hostable
SessionZero works fully offline by default, storing all your content and characters locally on your device. For shared, real-time play with friends, you have the option to run your own server instance. This means no central service is required, and your data ownership remains absolute.
Shared Sessions and Live Play
For Game Masters, Sessions allow you to track initiative, manage NPCs, and make real-time updates to player characters. Players can join your game, keep private journals, and reference the campaign's required Datasets. When online, updates are pushed instantly via WebSockets.
Open Source and Transparent
The code is licensed under AGPL-3.0. You're free to inspect, modify, and contribute to the project. There's no telemetry, no lock-in, and no hidden features—just community-driven TTRPG software built for TTRPG players.
SessionZeroDB
Every server instance includes a SessionZeroDB where users can download and share custom datapcks.
Federation (Future Plan - Phase 2)
The future plan is Federation: allowing independent SessionZero servers to discover and share public content (Datapacks, Templates) across any SessionZero server instance that is configured to allow public discovery. This enables players on one self-hosted server to connect with and use content from another public server they trust, without relying on a central authority.
Who Should Use This?
- Players and GMs who demand total control over their character sheets, notes, and game data.
- Anyone tired of apps that are bloated, restrictive, or constantly designed to sell you content.
- Developers or tinkerers who want a flexible, open-source platform to build their own TTRPG tools.