Zero-K
Overview
Zero-K is a free, open-source real-time strategy game — a Total Annihilation-style RTS running on the open-source Spring (Recoil) engine. It began as a fork of Spring Engine content with all proprietary assets replaced, and has since grown into a game in its own right, built around physically simulated projectiles, terrain manipulation and a flat technology tree.
Key Features
- 100+ unique units — every unit has a defined role and its own ability, from the nimble Glaive raider bot to the Jugglenaut that hurls invaders off your base.
- Physically simulated projectiles — shells, rockets and beams are simulated in flight, so fast units can dodge slow projectiles and hills block weapon fire, line of sight and radar.
- Terrain manipulation — terraform the battlefield with builders: dig canals to bring a navy inland, build ramps, bridges and fortresses, or crater the ground to bog down enemy tanks.
- Commander progression — you start with a construction-capable bipedal mech and unlock weapons and modules, including cloaking and resurrection, as you play.
- Campaign and co-op — non-linear single-player missions that unlock units in the order you choose, plus survival mode against waves of "chicken" aliens and several non-cheating AI opponents.
- Multiplayer up to 16v16 — ranked 1v1 ladder, team games, free-for-all, co-op against AI, and PlanetWars, a persistent clan meta-campaign fought out across planets.
- Powerful interface and Lua scripting — extensive use of Lua for the UI, gameplay enhancements and custom game modes, backed by thousands of community maps and mods.
- No monetisation — no in-game currency, no pay-to-win, no ads and no account needed for single-player.
Why Use Zero-K?
It is one of the most complete free RTS games available: more than a decade of refinement, a substantial single-player campaign, and multiplayer busy enough to fill 32-player battles nightly — all under the GPL. Because the engine is open source and scriptable, it is also a practical platform for anyone who wants to build their own RTS content.
Use Cases
- Playing a deep offline strategy campaign or survival missions.
- Fast 1v1 ladder games, or relaxed large team battles with friends.
- Long-running PlanetWars clan campaigns for persistent competitive play.
- Modding and scripting on an open engine with a public source tree.
Platforms
Official builds for Windows and Linux — free on Steam, with a semi-portable archive on itch.io for Linux users who prefer not to run Steam. The engine and game also compile from source on other platforms, but those builds are not officially supported. Cross-platform multiplayer works between the supported builds.
Licence
Free and open source — the game module is licensed under the GNU General Public License v2.0, and the Spring/Recoil engine it runs on is also GPL-licensed. The lobby and server infrastructure components use their own licences.
Similar Tools
- 0 A.D. — free and open source, another deep strategy game in the directory.
- Warzone 2100 — free and open source sci-fi RTS with unit design.