Rewrites, recomps and mashups explained
Passthrough mods have three cousins. What a Rust rewrite, a recomp and an in-game mashup are, and why most of them need your own game files.
The site tracks five kinds of project. Passthrough mods are the headline act, but they're part of a bigger wave of "making old games do new things".
Passthrough mods
Two real games run at once and talk to each other. See What is a passthrough mod?.
Rust rewrites
Someone writes the game's engine again, from scratch, usually in the Rust language with the Bevy game engine, and then loads the art, maps and sounds from your own copy of the original game.
The big example is IW4L, a from-scratch runtime for Call of Duty: Modern Warfare 2 (2009). Because the rewrite is new code, people can bolt anything onto it. The 2010 Rust Rewrite Mashup adds a Skate 3 skating mode and a real, endless Minecraft world to MW2. The Skate 3 Rust Engine recreates Skate 3's physics and tricks, and has since been dropped into Bully, GTA San Andreas, Garry's Mod and even World of Warcraft (via benilla, a from-scratch WoW 1.12 client).
Recomps and decomps
Older console games are being turned into native PC games:
- A decompilation ("decomp") turns the game's machine code back into readable source code, by hand or with tools. A matching decomp rebuilds the exact original bytes.
- A static recompilation ("recomp") translates the console code into code for your PC ahead of time, so it runs natively instead of in an emulator. Tools like N64Recomp, XenonRecomp (Xbox 360), the ReXGlue SDK and PSXRecomp do the heavy lifting.
The result: widescreen, high frame rates, mods and modern controllers, for games like Skate 3, Majora's Mask or Lost Odyssey. Recomps are also what made the Skate 3 Rust work possible: researchers learned how the game worked from them.
Recomps contain no game data. You supply your own legally obtained disc image or ROM.
In-game mashups
One game rebuilt or running inside another with a normal mod: no second game process. Think DOOM on ULTRAKILL's shop terminals, Minecraft players joining Hytale servers, or Steve as a character in Megabonk. Some are years old (Halocraft, Ocarina of Time in Minecraft); they're here because they're the same idea and people go looking for them together.
Tools
Launchers, catalogs, SDKs and kits for building or running all of the above, such as universal-modder (an AI-agent toolkit with a passthrough playbook) or the Passthrough launcher.
"Bring your own files": why it matters
Nearly every project here needs your own copy of the games involved. That's not a formality:
- It's what keeps these projects legal and online: they share their own code, never the games.
- Never download game files (ISOs, ROMs, "pre-installed" packs) from strangers. Besides being piracy, it's one of the most common ways malware spreads.
- If a project offers a download that "includes everything", treat it as a red flag. See Staying safe.