FAQ

Can I use it yet?

Yes, if you are a developer who wants a base to build on, or if you want to watch the project. No, if you need a server for players. A vanilla client of the same snapshot can join in offline mode, chat, run 20 commands and break blocks in creative. The world is not saved after you leave, only players are.¹ See Run a server and Status.

Will my plugins work?

No. Bukkit and Paper plugins do not load, and there is no facade API, because the project decided against one.² A loader for plugins as jar files, wasm or scripts does not exist either, and there is no decision about one yet. Today your code is a Rust Bevy plugin that you build together with the server, as in Minestom, where you write main yourself. You have to rewrite a plugin for mcrs, because it cannot be ported. See Not Paper and Paper to mcrs.

Why Rust?

Not because “it is faster”. Rust gives memory safety without a garbage collector. Each Bevy system declares which data it reads and which it writes, and the Bevy scheduler uses this to run systems in parallel without locks. The scheduler checks access conflicts when it builds the system graph. The compiler does not. The numbers we measured are in PERF.md, each with the machine and the scenario. See Parallel tick.

Another Rust server?

The server here is an application on top of a set of crates. The project differs in its process. Specifications come before code, the goal is parity with the real game, the measurement method is recorded and decisions are kept in the tracker. We publish no comparison with other servers.

Does it run on Linux and Windows?

The author measured and ran everything on macOS, on an Apple M4 Max with Metal. CI runs lint, clippy, portability checks and tests on Ubuntu 24.04, without the crates that need a GPU. For Windows the code has a jar path, and nobody has checked it.

Which game version?

One version, 26.4-snapshot-7, which is set in assets/minecraft/version.json. Old clients and worlds of other data versions do not work, and there are no datafixers.³⁴ The plan is to translate older client versions at the network edge.⁵

Is it legal?

Specifications are written by someone who may look at the game. Code is written from the specifications and has no game class names in it. The exception is world generation code, which was written without this rule. Textures and models come from the official client jar on your machine, and the repository contains no Mojang art. See Clean-room and docs/clean-room.md.

Is it safe to run?

Only on your own machine or on a trusted local network. The server has no authentication, so anyone can join under any name, and it listens on all network interfaces. Do not open the port to the internet.

Are there binaries?

Not yet. They will exist, but there is no issue for them. Until then you build from source, as Install the tools describes.

Can I publish my own plugin as a crate, or use mcrs crates?

Crates are not on crates.io, but you can depend on a git commit.⁶ There are no library examples yet.⁷ See Crates overview.

How do I follow progress?

Watch issues on GitHub, follow the tags feed or join Discord. The Status page lists every way.

Footnotes

1. WIP#78 Tracks saving changed chunks back to region files. ↩

2. Not planned#437 The decision that there is no facade or API crate, and the crates and plugins are the public surface. ↩

3. Not planned#388 The decision that saves are read at exactly the targeted data version, with no datafixers. ↩

4. Not planned#412 The decision to target one version at a time, with no backward compatibility. ↩

5. WIP#537 The decision that the network edge translates client protocols down to 1.21.6. ↩

6. Undecided#321 Tracks making the protocol, network and game data crates ready to publish. ↩

7. WIP#287 Tracks the minimal server, lobby and arena examples. ↩