RimWorld Trades Unity for Ludeon's Own Waylith Engine in Update 1.7

Ludeon Studios has pulled off one of the quieter but riskier moves an independent studio can make: swapping out the engine underneath an eight-year-old hit while it is still being actively played by millions. On October 12, the small team behind RimWorld announced update 1.7, which moves the colony sim off Unity and onto Waylith, an engine Ludeon built itself from the ground up.

The studio was careful to frame it as invisible to players in every way except speed. "The game looks and plays exactly the same, but in our tests performance is improved by 2-4x," Ludeon wrote in its announcement post. For a game whose entire identity is built on simulating dozens of colonists, hundreds of animals, and sprawling mod lists at once, that kind of headroom matters more than almost any other change the team could have shipped.

Why Build a New Engine at All

RimWorld has run on Unity since its 2013 prototype and 2018 full launch, and Unity's licensing turmoil in recent years has pushed more than one small studio to look elsewhere. Ludeon did not frame Waylith as a reaction to any single controversy, but the practical case was straightforward: full control over how the simulation ticks, loads, and renders, instead of working around a general-purpose engine built for very different kinds of games.

The studio credited an outside assist in getting there, thanking RocketWerkz, the Icarus and Stationeers developer, for sharing its Brutal framework during Waylith's development. It is a reminder that even a studio shipping one of the best-selling strategy games on Steam still leans on the wider independent development community to solve hard engineering problems.

The Numbers Ludeon Is Pointing To

Ludeon's own benchmarks, published alongside the announcement, are specific rather than vague marketing math. A stress test of a late-game colony showed 2.2x better performance on 1.7 compared with 1.6, and a modpack carrying 1,500 mods cut its load time from roughly 14 minutes down to 6. The studio was quick to add a caveat worth repeating to anyone expecting identical gains: individual results will vary with hardware and mod lists, and PCs older than about a decade may not run 1.7 at all.

Startup time, map and world generation, and general simulation speed are all faster across the board on Waylith, according to Ludeon, with the biggest gains showing up in exactly the scenario longtime players care about most: a heavily modded colony several in-game years deep, where Unity's overhead used to show.

What Actually Changes for Players and Modders

• Savegames are fully cross-compatible: a 1.6 save loads on 1.7, and a 1.7 save can be loaded back on 1.6 if a player switches branches.
• The vast majority of existing mods keep working without any changes from their authors; some will show a yellow "potentially unsupported" flag purely because the version number moved, not because anything actually broke.
• Modders get access to modern C# language features under Waylith, which Ludeon says makes complex, performance-heavy mods easier to write without dragging the simulation down.

Ludeon also thanked more than two dozen modders by name internally for testing early Waylith builds before this announcement, a detail that underlines how much of RimWorld's decade-long staying power runs through its modding scene rather than official content alone.

How to Try Update 1.7 Right Now

Update 1.7 is not yet the default version of the game. It is live on RimWorld's Steam "unstable" beta branch, reachable through the game's Properties menu and Betas tab, while the main branch that most players run stays on 1.6 for now. Full details are posted on Ludeon's own development blog, and the studio is routing bug reports through its official development Discord rather than Steam's review section.

That staggered rollout is itself a small-studio survival tactic: rather than flipping every player over to a rebuilt engine at once, Ludeon gets real-world performance data and mod-compatibility reports from its most engaged community members first.

A Second, Unannounced Game on the Same Engine

The update post closed with a line that will likely generate more conversation than the engine swap itself: "RimWorld isn't the only game on Waylith. We're working on something new!" Ludeon gave no further details on genre, platform, or timeline, and nothing beyond that single sentence has been confirmed, so anything beyond "a second project exists" remains speculation for now.

What is confirmed is that Waylith was built to outlast a single game. For a studio defined for years by one release, quietly building the infrastructure for a second project while still actively patching the first is as newsworthy as the engine swap that revealed it.