Foundry

Foundry (Foundry VTT) is a virtual tabletop platform for running tabletop role-playing games online — providing a shared digital game board, character sheets, dice rolling, and fog-of-war for remote or hybrid RPG sessions.

Unlike browser-based competitors, it's self-hosted (you run your own server, either locally or on a small cloud instance), giving game masters full control over their data and an extensive module/plugin ecosystem for customizing rules systems and automation.

Widely used in the tabletop RPG community (D&D and many other systems) as a paid, one-time-purchase alternative to subscription-based virtual tabletop platforms.