Mortar is a desktop mod manager for several games. It finds your game, installs its mod loader, keeps each set of mods in its own profile and launches the game with the profile you pick. Share a profile as a link and whoever opens it gets the same mods, with anything missing installed or queued.
The catalog covers Stardew Valley, Lethal Company, Valheim, Vintage Story, The Sims 4 and many Thunderstore games, with mods from Nexus Mods, GitHub, Thunderstore, CurseForge and the Vintage Story Mod DB. Mortar succeeds Concrete.
- Download from mortar.rethunk.tech/download, which has the steps for each channel: signed apt, dnf, pacman and Flatpak repositories, a Scoop bucket and a Homebrew tap.
- Or take a file from Releases: a Windows installer (x64 or ARM64), or for Linux an AppImage, portable program, Flatpak,
.deb,.rpmor Arch package. - The user guide covers requirements, SmartScreen on the unsigned Windows builds, first run, Nexus sign-in, profiles, backups and troubleshooting.
The optional browser extension (Rethunk-Tech/mortar-browser-extension) marks Nexus Mods pages with what a profile already has and hands Mod Manager Download clicks to Mortar; the user guide has its install steps.
Volunteers translate Mortar on Hosted Weblate; new translators are welcome.
To build it yourself:
bun install && wails3 devPrerequisites (including the wails3 CLI built from the pinned Wails fork), build and gate: HUMANS.md.
- Finds the catalog's games on Steam (including Flatpak Steam), GOG, Epic Games, the EA app, the Xbox app, Heroic, Minigalaxy, Lutris and Bottles, and installs each game's mod loader.
- Keeps each set of mods in its own profile, with install, update, rollback and share as a link or
.mortarfile. - Downloads from Nexus Mods, Thunderstore, CurseForge, GitHub and the Vintage Story Mod DB where a game lists them, and records files saved from Patreon posts and itch.io pages. It never re-hosts mod files.
- Edits a mod's config as a typed form, can keep a profile's saves separate, and shares profiles between your computers through a sync folder.
- A command line for the running app:
mortar games,mortar mods stardew "My Farm",mortar conflicts ..., with--jsonfor scripts. - Installs the Mortar SMAPI Bridge into each profile (console commands, Generic Mod Config Menu settings, a stream overlay). BepInEx games get the Mortar BepInEx Bridge instead, so Mortar can ask the running game which plugins it loaded.
 Problems: every problem on one page, one button to fix each |  Performance: what each mod costs at startup |
 Every mod scanned by your antivirus before it is installed | |
| Topic | Location |
|---|---|
| Using Mortar | docs/user-guide.md |
| How it works | docs/architecture.md |
| Decided work not yet built | docs/design.md |
| Screens and styling | docs/gui-design.md |
| Threat model | docs/security.md |
| Run, build, gate | HUMANS.md |
| Contributing | CONTRIBUTING.md |
| Security policy | SECURITY.md |
| Rules for agents | AGENTS.md |
| Licence | LICENSE |
Licensed under the GNU Affero General Public License v3.0.
Not affiliated with any game developer or mod site.