replicape

Everyone deserves a Mojang Developer cape.

Overview

Replicape is a tiny Bedrock relay that spoofs your Minecraft cape on the fly. It sits between your client and a remote Bedrock server, intercepts the player_skin packet, and replaces the cape with one you provide (default: MojangStudios_cape.png). It also dumps your original cape to disk for convenience.

Tested with bedrock-protocol Relay on 1.21.100. Your mileage may vary if Mojang changes packet structures.

What it does (in one breath)

• Runs a bedrock-protocol Relay that listens on 127.0.0.1:19130 and forwards to a destination server (default: suomicraftpe.ddns.net:19132).
• Preloads your replacement cape from MojangStudios_cape.png using sharp, ensures RGBA, and stores {width, height, raw} in memory.
• On player_skin, flips switches to look “premium/persona-off/cape-on-classic”, swaps skin.cape_data with the preloaded image, tweaks persona cape piece IDs, and notifies you in chat with a “Cape Spoofer activated” system message.
• If you connected with a cape, it will try to save your original cape to original_cape_<timestamp>.png for posterity.

Why this exists

For folks who want to test cape looks, branding, or texture alignment without touching resource packs on disk or running a modded client. It’s a protocol shim that rewrites exactly one thing: your cape in the player_skin packet.

Requirements

• Node.js 18+ (LTS recommended)
• A working C/C++ toolchain if your OS needs it for sharp (libvips). See Troubleshooting.
• A valid PNG at MojangStudios_cape.png with the expected cape dimensions (common 64x32 or 64x64; any RGBA with alpha works).

Install

npm i -g replicape-mc

Quickstart

1. Point your Minecraft Bedrock client to localhost port 19130 (that’s where the relay listens).

2. Start the relay.

   node replicape.js

3. Join. If the connection succeeds, you should see logs like:

   Creating relay New connection 127.0.0.1:xxxxx Cape spoofed with MojangStudios_cape.png (64x32) Cape Spoofer activated

4. Check your in-game appearance. The system message should pop once per skin send.

Configuration

The relay is configured inline. Adjust these knobs in createRelay():

• version: Bedrock protocol string. Example: 1.21.100. Must match your client. If you’re not sure, run the relay with omitParseErrors: false to see parsing failures. Defaults to latest stable release.
• host / port: Where the relay listens (default 127.0.0.1:19130). Keep it local unless you know what you’re doing.
• destination.host / destination.port: The remote Bedrock server you actually want to join.
• offline flags: Leave false for normal Xbox Live authentication flows.

You can also change the default cape PNG by renaming or modifying loadCapeData() to point at a different file.

Environment variables (optional)

Not strictly required, but if you prefer env-driven config, wrap these in your script:

• REPLICAPE_LISTEN_HOST (default 127.0.0.1)
• REPLICAPE_LISTEN_PORT (default 19130)
• REPLICAPE_DEST_HOST (default suomicraftpe.ddns.net)
• REPLICAPE_DEST_PORT (default 19132)
• REPLICAPE_VERSION (defaults to latest stable release)
• REPLICAPE_CAPE_PATH (default MojangStudios_cape.png)

How it works

• On startup, sharp reads MojangStudios_cape.png, converts to raw RGBA, and caches {width, height, data} in spoofedCapeData.
• The relay emits serverbound events for packets sent to the server. When it sees player_skin:
  • It marks the skin as premium, persona=false, cape_on_classic=true.
  • If the client sent a real cape, it reconstructs it via sharp and saves it to original_cape_<timestamp>.png for you.
  • It replaces params.skin.cape_data with your preloaded image.
  • It aligns persona-cape pieces (product_id, piece_id, pack_id) so servers that sanity-check persona pieces don’t immediately nuke the change.
  • It queues a text system message confirming activation.
• Everything else passes through unmodified (except for dropping some noisy logs).

Notes and caveats

• Protocol/version drift: If your client updates, the declared version may need to change. Packet layouts can and do drift.
• Servers with stricter checks may ignore/override skin mutations or enforce canonical capes via server-side policies.
• PNG dimensions: Use a known-good cape size, keep alpha, and mind that some clients expect specific layouts.
• Saving original capes: Works only if the incoming cape_data is present and includes width/height + RGBA data.

Troubleshooting

• sharp install fails on Linux

  • Ubuntu/Debian: sudo apt-get update && sudo apt-get install -y build-essential pkg-config libvips
  • Alpine: apk add --no-cache vips-dev build-base python3
  • RHEL/CentOS: sudo dnf install -y gcc-c++ make pkgconfig vips-devel
  • Then reinstall: npm rebuild sharp

• Relay starts but client can’t join

  • Verify your client points to 127.0.0.1:19130.
  • Make sure the destination server is online and reachable from your machine.
  • Check firewalls; ensure UDP/19132 and your local listen port are open locally.
  • Match the protocol version with your client build; if mismatched, you’ll see parse/handshake issues.

• “Spoofed cape data not loaded yet”

  • The PNG failed to load, or the path is wrong. Confirm MojangStudios_cape.png exists next to the script and is a valid RGBA PNG.
  • Try another PNG to rule out a broken image.

• Original cape didn’t save

  • Not all clients send a cape blob. Ensure you had a cape equipped when connecting.
  • Check write permissions in the working directory.

Extending

• Hot-reload the cape: watch the file and rebuild spoofedCapeData on change.
• Per-player capes: map XUID -> PNG path for multiplayer testing.
• CLI flags/env config: promote inline constants to a config module or yargs/commander CLI.
• Validation: assert PNG dimensions and channel count up front with helpful errors.

Legal & Fair Use

• This project mutates your own outbound skin/cape data at runtime. It does not patch game files or distribute copyrighted assets.
• Respect server rules and Mojang/Microsoft EULAs. Some servers may prohibit cosmetic spoofing.
• You are responsible for how you use this tool.

Minimal script shape (for reference)

This is the rough structure your script should follow. Names and IDs are the same as in the example you provided.

const { Relay } = require('bedrock-protocol')
const sharp = require('sharp')

let spoofedCapeData = null

async function loadCapeData() { /* read PNG via sharp -> raw RGBA -> store {width,height,data} */ }
function createRelay() { /* start Relay, intercept player_skin, swap cape, send system text */ }

loadCapeData().then(createRelay)

FAQ

• Q: Will this work on Realms or Marketplace servers?

  • A: If they allow direct IP and don’t enforce stricter skin integrity checks, possibly. Many curated servers will likely block altered cosmetics.

• Q: Can I use JPEG or WEBP for the cape?

  • A: Use PNG with alpha. The relay converts and sends raw RGBA that should match client expectations.

• Q: Can I change other skin parts?

  • A: Yes, the same approach can rewrite other skin.* fields, but expect server pushback if you get creative.

License

MIT. No warranty.

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