Design star systems, prescripted empires, origins, events and anomalies — then export directly to mod-ready files. No install required.
Stellaris mods are written in Paradox's own script format — plain text files with strict, cross-referenced rules that live across dozens of game files: which traits a species archetype can take, how many trait points a Gestalt empire gets versus an organic one, which ethics combinations are actually legal, what a valid event chain needs to compile. None of that is validated as you write it. You find out something's wrong when the mod fails to load, or worse, when it loads but behaves incorrectly in-game.
Building a full custom empire, a chain of anomalies, or a set of prescripted species by hand means holding all of those rules in your head at once, or discovering the ones you missed through trial and error.
Stellaris Mod Builder is a visual, form-based editor for the content types that make up a Stellaris mod. You build systems, empires, origins, events, anomalies, archaeology sites and astral rifts through structured forms instead of raw script, and the tool checks your work against the game's actual rules — trait budgets by species archetype, forbidden trait combinations, ethic and authority compatibility, and more — before you ever export. When something would be invalid in-game, you find out on the page, not after a failed load.
Everything runs entirely in your browser. Nothing you build is uploaded anywhere — your projects are saved locally on your device, and exporting produces mod-ready files you place directly into your Stellaris mod folder.
Star systems, prescripted empires, origins and species — built and validated against the same rules the game engine enforces.
Event chains, anomalies, archaeology sites and astral rifts, structured without hand-writing the underlying script.
A full catalog of weapons, armor, shields, reactors and thrusters to draw from when building custom designs.
Trait-point budgets, forbidden combinations, and cross-file rule checks run before export — not after a failed load.
Produces mod-ready files, packaged and ready to drop into your Stellaris mod folder.
Runs entirely client-side. Your projects are saved locally in your browser and never leave your device.
Opens in a new tab. No install, no account, no upload.