MultiLogin Compat Mod
A Fabric server-side mod for Minecraft 1.21.1(maybe other versions) that integrates with project MC-MultiLogin-service.
I don't know my version or loader
mc-multilogin-compat-mod
A Fabric server-side mod for Minecraft 1.21.1 (Mojang mappings) that integrates with MC-MultiLogin-service.
一个用于 Minecraft 1.21.1（Mojang 映射表）的 Fabric 服务端模组，用于与 MC-MultiLogin-service 集成，可以实现多源登录方式。
We suggest you to use this with Authlib-Injector. This mod only change the login method and the login-failed message.
建议配合 Authlib-Injector 使用。此模组仅修改登录方式和登录失败时的提示信息。如果您使用Authlib-Injector，请记得设定它的链接为 MC-MultiLogin-service提供的API地址。
Velocity Plugin Version
Config can be found at plugins\multilogin-auth-compat\multilogin-compat-config.json.
配置可以在plugins\multilogin-auth-compat\multilogin-compat-config.json找到。
Fabric Mod Version
Features
- On every player login the mod calls the configured MC-MultiLogin-service endpoint with
detail=true, so authentication failures return a structured JSON error instead of the generic "Failed to verify username!" message. - Detailed error reasons (
DUPLICATE_NAME,BANNED,NOT_FOUND, …) are forwarded directly to the connecting client in the disconnect screen. - Auto-rename on
DUPLICATE_NAME(configurable): when the service reports that a player name is already taken by another skin-site account, the mod automatically retries the login with the service-suggestedavailableId(e.g.Steve_2) and records the original → new-name mapping inconfig/mc-multilogin-renames.json.
Setup
- Place the mod JAR in your server's
mods/directory. - Start the server once – a default config file will be generated at
config/mc-multilogin-compat.jsonand the server will stop with an error asking you to fill in the API URL. - Edit the config and set
apiUrlto the base URL of your MC-MultiLogin-service method entry (e.g.http://127.0.0.1:25600/login/my). - Restart the server.
Configuration (config/mc-multilogin-compat.json)
{
"apiUrl": "http://127.0.0.1:25600/login/my",
"autoRename": true
}
| Field | Type | Default | Description |
|---|---|---|---|
apiUrl |
string | "" |
Required. Base URL of the MC-MultiLogin-service login method (e.g. the path configured under method[].url). The mod appends /session/minecraft/hasJoined?… automatically. |
autoRename |
boolean | true |
(Not working at present) When true, a DUPLICATE_NAME rejection triggers an automatic retry using the availableId returned by the service. The rename is persisted in config/mc-multilogin-renames.json. Set to false to disable and show the error instead. |
Building
# Requires Java 21 and internet access to maven.fabricmc.net
./gradlew build
The output JAR will be in build/libs/.
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.16, 1.16.1, 1.16.2
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on Modrinth — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — How to install Minecraft Java mods & modpacks walks through it step by step.
- Ships as mc-multilogin-compat-velocity-1.0.0.jar — drop this file into the mods folder
- Download size: 18 KB
- Download link checked 29 Sept 2026 — working
These come from our own check of the pack file, not from the source page.