Nat20.cloud is a free online platform for running tabletop role-playing game sessions. It supports games such as Dungeons and Dragons and Pathfinder, and it does not require a subscription or paywall. The platform is designed to function as a standalone GM screen, allowing a game master to use it at a physical table without any players connected, or to run sessions remotely with a group. Players can join a session by sharing a link and signing in with a free account, with no software installation needed. The platform includes a set of integrated tools. A combat tracker manages initiative order, hit points, conditions, and turn progression. A dice roller supports all standard dice from d4 to d100, with macros for common rolls, and is available both in-session and as a public standalone tool. A battle map lets users place tokens, track positions, and run encounters on a grid, and it is optimized for touchscreens and tablets. Session notes can be written and organized, and a reference library provides access to official D&D 5e SRD content, including spells, monsters, conditions, feats, and class features, as well as the Pathfinder Second Edition ruleset with ancestries, backgrounds, and classes. Users can also create and share their own homebrew rulesets with the community. The campaign editor allows game masters to build shops with items and prices, group scenes into acts, and arrange them on a board view with drawn paths between scenes. Scene writing supports structured elements such as read-aloud boxes, skill checks, treasure callouts, and GM-secret blocks that can be hidden from players and revealed live during a session. Content fields that reference other items are clickable, enabling quick navigation between characters, classes, spells, and other entries. All features are accessible within a single browser tab, and the platform is free to use indefinitely.