Account Management
Set up Microsoft, offline, Authlib Injector, or trial accounts — and bind different accounts to different instances.
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Account Types
Polymerium supports four types of accounts:
| Type | Use Case | Authentication |
|---|---|---|
| Microsoft | Full multiplayer, Realms, servers | Device Code Flow → Xbox Live → Minecraft API |
| Offline | Local / single-player, no server access | Username only, generates a deterministic UUID |
| Authlib Injector | Third-party authentication servers | Yggdrasil protocol with -javaagent injection |
| Trial | Quick start — try the launcher without signing in | Built-in demo accounts with fixed roles (available without any Microsoft account) |
Adding Accounts
Go to the Accounts page in the sidebar. Click Add Account and choose the type:
Microsoft Account
- Polymerium shows a device code (e.g.
A1B2C-3D4E5). - Open microsoft.com/link on any device and enter the code.
- Sign in with your Microsoft account.
- Polymerium automatically detects the login and fetches your Minecraft profile.
Your tokens are stored locally and refreshed automatically when they expire.
Offline Account
- Enter a username.
- That's it. Polymerium generates a deterministic UUID based on the name.
Offline accounts can't join servers that require authentication, but they work perfectly for single-player and LAN.
Offline accounts are available only after you've added a Microsoft account. If you just want to try the launcher without signing in, use a Trial account instead.
Trial Account
Trial accounts are pre-made with fixed roles — quick to pick up and play without any setup. No Microsoft account needed.
They work for local and single-player play only, but they're enough to try out the launcher before committing to a full sign-in.
Authlib Injector Account
- Enter the server URL of the Yggdrasil authentication server (e.g.
https://auth.example.com/api/yggdrasil). - Polymerium fetches the server metadata and injects the appropriate
-javaagentflag at launch. - Sign in with your credentials for that server.
This is useful for Chinese Minecraft communities that use third-party auth servers.
Per-Instance Account Binding
By default, your selected default account is used for all instances. But you can override this per instance:
- Open the instance's properties.
- Set the account override to any of your added accounts.
This lets you use different accounts for different servers or game modes without switching globally every time.
Token Refresh
- Microsoft accounts are refreshed automatically via OAuth token refresh — you won't need to re-login.
- Authlib Injector accounts are validated and refreshed using the Yggdrasil protocol before each launch.
If a token can't be refreshed (e.g. you revoked access), Polymerium will prompt you to re-authenticate.
Account Data Storage
All account data is stored in the local SQLite database. Credentials are never uploaded anywhere. The only network calls are to Microsoft/Yggdrasil auth servers for token operations.