RimWorld 1.7 swaps Unity for Waylith — beta available now

RimWorld 1.7 is moving the colony sim from Unity to Ludeon’s own Waylith Engine. Announced on October 12, the update is already available on Steam’s unstable beta branch. The main branch remains on 1.6.

Ludeon says the game keeps its existing look and gameplay, with performance gains of two to four times in its tests. For big colonies or long mod lists, the questions are practical: will it run faster, will your saves and mods work, and how do you try the beta? Your colonists can still make terrible decisions. The engine may process them faster.

The update at a glance

RimWorld 1.7 performance: loading, map generation and simulation

The developer reports improvements to startup, loading large mod lists, map and world generation, and simulation ticks per second. Two examples give the headline some context: a late-game colony ran 2.2 times faster, while a 1,500-mod setup loaded in six minutes instead of fourteen.

Ludeon’s tests, announced October 12, 2026. Results vary by hardware and mods.

Those are Ludeon’s results. Your hardware and mod list can change the outcome, so “four times faster” is no promise for every colony. Ticks per second describe how quickly the simulation advances. That matters when your colony has more colonists, animals and jobs to process; a smoother camera alone would not solve a slow-running colony.

Save compatibility and the yellow mod warning

According to Ludeon, saves work in both directions between 1.6 and 1.7. The studio also expects the vast majority of mods to work without changes. A yellow compatibility warning can simply mean a mod has not yet been marked for the new version; it does not, by itself, prove the mod is broken.

That leaves room for exceptions. Before testing the beta, make a separate save backup and check the current notes for the mods your colony depends on. Treat compatibility as something to verify with your own setup, rather than a reason to skip the backup.

There is also a hardware caveat: Ludeon warns that computers more than ten years old may not run 1.7. That is a warning about possible incompatibility, not a complete new system-requirements list.

What Waylith changes for modders

Waylith is an in-house engine built by Ludeon Studios. The studio says modders can use the latest C# language features, build complex mods with less impact on performance, and make larger visual changes or custom effects more easily.

These are possibilities for mod authors, rather than new features automatically added to your mod list. If you make a mod, Ludeon asks you to test it on 1.7 and then mark the release as compatible. That removes the version warning for players. The studio credits more than two dozen modders with testing the engine before this announcement.

How to access the RimWorld 1.7 unstable beta

Open RimWorld’s Properties from your Steam library and switch the beta selection to unstable. If the download does not start, restart Steam. When a version picker appears at launch, use Play 1.7 Unstable.

Test a backed-up colony with the mod list you actually use. If something stops working as it did in 1.6, Ludeon asks for reports through the official RimWorld development Discord linked in the announcement.

If you want to carry on with your current colony without joining beta testing, you can stay on the main branch, which remains on 1.6. The announcement gives no date for the stable 1.7 release.

Ludeon is also working on something new

The studio says another game is being built on Waylith, but has not shared its name, gameplay or release date in this announcement. There is nothing here to turn into a RimWorld sequel announcement.

The immediate decision is simpler: try the beta if you want to test the new engine with your colony and report problems; stay on 1.6 if you would rather wait. For large colonies and heavy mod lists, the developer’s results make this an update worth watching.

Sources

Ludeon’s announcement, October 12, 2026 · Official Ludeon post with the same announcement · Steam announcement