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FAQ

The most common questions from everyday use. No answer here? See Report an issue.

Launching and Java

“No Java runtime detected” Go to Settings → Java runtime → click Quick scan to detect system Java automatically; if none is found, click Download to install it online. The launcher needs four core runtimes — Java 8 / 17 / 21 / 25 — and picks the right one for each game version automatically. The game crashes right after launching Use Log analysis to paste the log or analyze the crash report directly. Common causes are mod conflicts, insufficient memory, and a mismatched Java version. Out of memory (OutOfMemoryError) Increase the memory allocation: Settings → Java runtime → Default configuration → Memory allocation. Large modpacks do well with 6–8GB; see Performance tuning.

Accounts

Microsoft login says the token expired Microsoft login tokens have a limited lifetime. Once expired, the launcher shows a reauthorization window; log in once more. “Account data file is corrupted or the machine code changed” Account data is encrypted and bound to the machine, so it cannot be decrypted after reinstalling the system or changing hardware. The data has already been cleared automatically; simply add the account again. An offline account cannot join a server Offline login cannot join servers that require genuine verification. For external login servers (LittleSkin / Tongyitong), log in with the corresponding method.

Downloads and resources

Downloads are slow or fail
  • Make sure the matching auto-select switches are on in Settings → Download settings (Automatically select the fastest download source / Automatically select download source / Automatically select the fastest resource download source)
  • Try replacing the mirror domain manually; see Download mirrors
  • If you use a proxy, check the proxy configuration in Network settings
Resource search returns nothing Check that the filters (game version / loader) match what you expect. CurseForge and Modrinth do not index the same content, so try switching the source and searching again.

Multiplayer

NAT detection fails or it never connects This is common on restricted networks (corporate or campus). Try a phone hotspot; see Multiplayer for details. Multiplayer misbehaves after installing Radmin VPN / Hamachi Virtual network adapter software like this competes for routes. The launcher already avoids the common problems, but if issues persist, exit them first.

Interface

The UI stutters and animations drop frames Settings → Appearance: lower Component material (liquid glass and acrylic are the most expensive), turn off animation or make it faster, and limit the maximum frame rate. How do I change the background image or accent color? Settings → Appearance: the background supports custom images and blur; the accent color supports custom values and “follow background” (Monet color extraction).