Simple Login



SimpleLogin is a forge mod aimed to protect servers in offline mode.


SimpleLogin is similar to some auth plugins in bukkit like AuthMe: the mod will check player's password when they log in.

However, there are some differences: instead of inputting the password using a command, passwords are stored in a specific file at the client-side and automatically sent to the server when the player joins, so that players don't have to input the password every time. Besides, the client will let you choose a password during the first launch, so in most cases, players won't even need to do anything.


Put the simplelogin-xxx.jar into the mods directory on both server-side and client-side.

Getting started

You don't need to configure anything if you don't care much.

Players' password does not need to be inputted manually, instead, the client would generate a random UUID as the password and save it in .minecraft/.sl_password, and send it to the server when joining.

The server will remember the player's password when he joins for the first time, and when he joins later the server will check if the password matches the first one.


Is my password safe?

Sure, the password is hashed using SHA256 at the client-side and hashed using BCrypt before storing at the server-side. However, the password is stored without any encryption at the client-side, so be careful don't copy .minecraft/.sl_password file when sharing your client with others.

What should I do if I want to change the client?

You should backup your minecraft/.sl_password file and copy it to your new client.

Storage providers

There are various ways to store the user data at the server-side and each has its benefits and shortcomings. Simple Login provides an abstract layer to allow different storage implementations. Each implementation is called a "storage provider".

Each storage provider has its unique resource location (e.g. simplelogin:file) to identify itself.

Simple Login itself provides two storage providers: file and sqlite.

File storage provider

ResourceLocation: simplelogin:file

File storage provider is the simplest implementation of the storage provider interface, which stores all the user data as JSON format at world/sl_entries.dat.

SQLite storage provider

ResourceLocation: simplelogin:sqlite

SQLite storage provider might be more efficient than the file provider, but it needs an SQLite JDBC connector which has roughly 6 MB and I decided not to bundle it in Simple Login. Therefore, if you want to use this provider, you'll need to install a JDBC connector yourself. The simplest way to do that is to download it and copy org/sqlite and META-INF/services directories into Simple Login mod jar.

Custom storage providers

If you're familiar with Java and forge mods, it won't be very hard.

You need to implement the top.seraphjack.simplelogin.server.storage.StorageProvider interface, and register your own provider before the server starts by calling top.seraphjack.simplelogin.server.SLRegistries.STORAGE_PROVIDERS::register.

Simple Login plugins

Simple Login plugins, or plugins for short, is an extension to how Simple Login handles when players join, log in and leave the server.

Just like storage providers, each plugin has its unique resource location to identify itself.

Some key functionalities of Simple Login are also implemented as built-in plugins, and here's a list of them.


ResourceLocation: simplelogin:autosave

This plugin will trigger the Storage provider to save all data every five minutes.

This plugin is enabled by default.


ResourceLocation: simplelogin:protect_coord

This plugin will teleport players back to the spawn point before they leave the server, and teleport them back when they successfully logged in, thus prevents possible position leakage by unauthorized log-in attempts.

This plugin is disabled by default since its behavior will cause some problems when playing large modpacks.


ResourceLocation: simplelogin:resend_request

This plugin will ask the client to log in every five seconds if by some mistakes their previous log in packet unable to arrive the server.

This plugin is enabled by default.


ResourceLocation: simplelogin:restrict_game_type

This plugin will change the player's game type to spectator when they leave or join the server, and change their game type to their default game type (stored in storage providers) when then log in successfully.

This plugin is enabled by default.


ResourceLocation: simplelogin:restrict_movement

This plugin will prevent players from moving around before login.

This plugin is enabled by default.


ResourceLocation: simplelogin:timeout

This plugin will kick players who haven't authenticated after a while (default is 600 seconds, can be changed in Simple Login's configuration in <server>/<world>/serverconfig/simplelogin-server.toml). The timeout value used to be 60 seconds but has been increased to 600 seconds after issues with large modpacks causing the synchronization upon login to take longer than a minute.

This plugin is enabled by default.


All commands have auto-complete support.

  • /simplelogin unregister <PlayerName>

    • Unregister the player
  • /simplelogin save

    • Save all player entries
  • /simplelogin setDefaultGameType <PlayerName> <GameType>

    • Configure the after-login game type for the player
  • /simplelogin about

    • Show the version information
  • /simplelogin plugin available

    • Show the list of available plugins
  • /simplelogin plugin loaded

    • Show the list of loaded plugins
  • /simplelogin plugin load <ResourceLocation>

    • Load the specified plugin
  • /simplelogin plugin unload <ResourceLocation>

    • Unload the specified plugin
  • /sl_change_password <NewPassword>

    • Change password to NewPassword
    • This command is implemented on client-side for security reasons


Server Configuration

  • secs: Integer

    • Time to wait for player to authenticate, if no successful authentication happened after this long the player will be disconnected.
    • Default 600 seconds.
    • Used to be 60 seconds but was increased to 10 minutes because of timeout issues with large modpacks.
  • plugins: String Array

    • plugins to load by default.
  • commandNames: String Array

    • Commands that are allowed to be executed by a player before they log in.
    • Note that you need to specify full command without the heading /, such as give @p minecraft:apple 16
  • storageProvider: String

    • The storage provider to use.
  • defaultGameType: Integer

    • Default game type for newly registered users.
    • 0, 1, 2, 3 represents survival, creative, adventure and spectator.