Do these three things first
- Keep the complete error, instance name, game version and recent changes.
- Back up important worlds. Do not start by deleting the instance or data folder.
- Inspect the task and game window to distinguish preparation, a started game and an actual failure.
| Stage | Check first |
|---|---|
| Account validation | Account validity, application registration or service-access error |
| File download | Source, network, free space and the specific failed file |
| Java selection | The instance requirement and the selected runtime |
| Mod loading | Versions, loader, dependencies and recent changes |
| World loading | World version, missing mods and files in use |
| Joining a server | Address, identity, matching client and server message |
Interrupted downloads
Inspect the exact source in the task. Retry after the network recovers. Existing files may be reused or downloads resumed where possible. A source without resume support or inconsistent data can require a fresh download.
If one platform is unavailable, local content can still be managed. Do not delete the whole instance to retry one file.
Java or memory errors
Check instance-specific Java before the global default. Old and new games can need different runtimes. Use instance preparation or Java management.
For allocation errors, close unnecessary programs and check manual limits against advanced arguments. Do not assign all physical memory to Minecraft.
Failure after adding mods
Check the game version, loader and missing dependencies. First disable recently added content supported by the evidence, changing one clear group of factors at a time.
Do not remove world-dependent mods and then save your only world. Use a copy while keeping the original environment. Read Mod installation.
A window opened but the game is not ready
Initial loading, mod initialization and resource reloads may continue. Watch the actual game and task. Do not launch again just because a process has been created.
If it remains unresponsive, preserve the logs. Close normally if possible. Force-ending can interrupt saving, so use that action only after understanding the situation.
Locked or incompatible worlds
Make sure another game is not using the same world. Do not delete lock files to bypass an active save.
A newer world or one missing mods may not load in an old environment. Keep the original, return to a matching environment or restore a backup. Read World management.
Server joining fails
“Game started” does not mean a successful server join. Read the actual disconnect message and check account, address, version, allowlist or operator requirements. See Servers.
Ask AI to analyze
If error details offer Analyze and repair with AI, continue with a configured model. The flow uses this instance and failure record to gather evidence, prepare a limited repair and observe a new run.
A passed initialization check still needs verification in the original scenario. Use Undo if the attempt is unsuitable. Read AI repair.
Still unresolved
Use Feedback and logs to provide steps, complete errors and relevant logs, hiding credentials and private addresses. Naming the failed stage helps more than “it will not open.”