Minecraft Errors and How to Fix Them
Crashes and errorsWhat does the message mean that prevents the game from launching on a server, kicks a player off, fails to start, or crashes — and what should players and server owners do? The texts are taken directly from the game.
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- Failed to verify username!
- Client incompatible
- Cannot connect to the server
- Timeout exceeded
- Insufficient memory
- UnsupportedClassVersionError
- You need to agree to the EULA
- FAILED TO BIND TO PORT
- You're not on this server's whitelist!
- Network protocol error
- You are already logged in somewhere else
- Invalid session
Game end code
| Error | In English | What does it mean? |
|---|---|---|
 Exit Code 1 — error code 1 | Exit Code 1 | Minecraft crashes with code 1: find latest.log, check Java and mods. Examples of errors and free log analysis without registration |
Can't connect.
| Error | In English | What does it mean? |
|---|---|---|
 Cannot connect to the server | Can't connect to server | The game could not reach the server: no response was received at that address. |
 Unknown server | Unknown host | The game could not find that address: no server exists for that name in DNS. |
 Timeout exceeded | Timed out | The server did not respond in time, and the game terminated the connection. |
 Connection lost | Connection Lost | Connection to the server has been lost. This is the window header — the reason is written below in a line. |
| End of stream | End of stream | The server disconnected during data exchange without explaining why. |
Version and mods
| Error | In English | What does it mean? |
|---|---|---|
 Network protocol error | Network Protocol Error | The game received data from the server that it could not parse. |
| Client incompatible | Incompatible client! Please use | The game version does not match the server version. The server will specify the required version — use that one. |
 Incomplete tag set received from the server | Incomplete set of tags received from the server. Please contact a server operator. | The server sent an incomplete set of block and item tags — usually due to mods or data packs. |
Account and login
| Error | In English | What does it mean? |
|---|---|---|
 Failed to verify username! | Failed to verify username! | The server checks Mojang's license for servers, and your account failed verification. |
| Invalid session | Invalid session (Try restarting your game and the launcher) | The account login token has expired, and Mojang servers did not accept it. |
| Online game is disabled | Multiplayer is disabled. Please check your Microsoft account settings. | Online game is disabled in your Microsoft account settings — usually for a child account. |
| Authentication servers are unavailable | Authentication servers are down. Please try again later. Sorry! | Mojang login servers are not responding — neither to you nor to the server when verifying your account. |
| Account blocked for online play | Your account is permanently suspended from online play | Account blocked by Mojang for online play — on any servers and in Realms. |
The server will not allow entry
| Error | In English | What does it mean? |
|---|---|---|
 You're not on this server's whitelist! | You are not white-listed on this server! | On the server, a whitelist is enabled, and your username is not in it. |
| You are blocked on this server | You are banned from this server | The administrator has banned you on this server — by username or IP address. |
 The server is full! | The server is full! | The server is full. |
| You are already logged in somewhere else | You logged in from another location | Players reconnected to the server under your username, and the server dropped the old connection. |
 The server requires acceptance of the behavior code. | Server requires accepting the Code of Conduct | The server displays its rules upon login and only allows those who accept them. |
 The server does not accept external players | This server does not accept transfers | You were redirected to this server from another one (via command /transfer), but this server doesn't accept such transfers. |
 The server requires a special set of resources. | This server requires a custom resource pack | The server requires a resource pack, and you have declined it or it failed to load. |
Kicked from the server
| Error | In English | What does it mean? |
|---|---|---|
 Flights are disabled on this server | Flying is not enabled on this server | The server determined that you are flying, and flying is disabled on this server. |
| You've been inactive for too long! | You have been idle for too long! | You haven't done anything for longer than the server allows, and it has kicked you. |
| You have been kicked by an operator | Kicked by an operator | You were kicked by an operator using the /kick command. This is not a ban — you can rejoin. |
 You have been kicked for spam | Kicked for spamming | The server detected that you are typing in chat or entering commands too frequently. |
| Excluded due to packet frequency | Kicked for exceeding packet rate limit | The client sent the server too many packets per second. |
| Too long a connection | Took too long to log in | The connection took too long, so the server closed it. |
Chat
| Error | In English | What does it mean? |
|---|---|---|
| Chat disabled in account settings | Chat is not allowed by account settings. Press '' again for more information. | Chat is disabled by Microsoft account settings: you cannot send or read messages. |
| The profile key's validity period has expired | Expired profile public key. Check that your system time is synchronized, and try restarting your game. | The chat signing key has expired — usually due to incorrect computer time. |
| Chat message validation error | Chat message validation failure | The server failed to verify the chat message signature and kicked you. |
| Cannot check chat messages | Chat messages can't be verified | This is not an error, but a warning: chat messages on the server are not verified by signature. |
The game fails to start or crashes.
| Error | In English | What does it mean? |
|---|---|---|
 Insufficient memory | Out of memory! | The game ran out of the memory allocated at startup and crashed. |
 Could not reserve enough space for object heap | Error occurred during initialization of VM. Could not reserve enough space for object heap | Java couldn't allocate the amount of memory specified in the -Xmx parameter, and the game failed to start. |
 UnsupportedClassVersionError | java.lang.UnsupportedClassVersionError: … has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 61.0 | Java is older than required for this game or server version. The numbers in the error are class file versions: 65 — Java 21, 69 — Java 25. |
 No supported graphics backend was found | No supported graphics backend was found. | The game could not find a way to render on this graphics card and will not launch. |
 Graphics device not supported | Graphics Device Unsupported | The map does not support the selected graphics mode — usually 'Amazing!' |
 Data set errors | Errors in the currently selected data pack(s) prevented the world from loading. You can either try to load it with only the vanilla data pack ("Safe Mode"), or go back to the title screen and fix it manually. | The world's data pack is corrupted and the world will not load with it. |
 Problems reading the world folder | The following issues occurred while trying to read world folder "". It might be possible to restore the world from an older state or you can report this issue on the bug tracker. | The game could not read world files and suggests restoring from a previous state. |
Mods and crash reports
| Error | In English | What does it mean? |
|---|---|---|
| Incompatible mods found! | Incompatible mods found! | The mod loader found mods that are missing something or conflicting with each other and did not launch the game. |
 Mixin apply failed | Mixin […] from phase […] in config […] FAILED during … | The mod failed to integrate into the game's code (Mixin) and the game crashed on startup. |
| duplicate mod | duplicate mod … | In the mods folder, two files from the same mod — the mod loader doesn't know which one to take and stops. |
 A mod crashed on startup! | A mod crashed on startup! | One of the mods crashed during startup, and Fabric halted the loading process. |
 Ticking entity | Ticking entity | The game crashes when processing one entity or block with data — such as a chest, furnace, or hopper. It will crash again as soon as that chunk of the world is loaded. |
The server will not start
| Error | In English | What does it mean? |
|---|---|---|
| You need to agree to the EULA | You need to agree to the EULA in order to run the server. Go to eula.txt for more info. | The server will not start until you accept Mojang's license agreement (EULA). |
 FAILED TO BIND TO PORT | **** FAILED TO BIND TO PORT! | The server port that is already in use — usually by a second server running on the machine. |
| A single server tick took too long | A single server tick took {} seconds (should be max {}) | One server tick lasted longer than `max-tick-time`, and the guard stopped the server, deciding it had frozen. |
| Failed to load datapacks | Failed to load datapacks, can't proceed with server load. You can either fix your datapacks or reset to vanilla with --safeMode | The server failed to load world data packs and will not start. |
| Exception in server tick loop | Exception in server tick loop | The server crashed during operation: an error in one tick caused a complete shutdown. |
 Failed to load world data | Failed to load world data. World files may be corrupted. Shutting down. | The server failed to read world files and shut down. |
GLFW, OpenGL, and older Java versions
| Error | In English | What does it mean? |
|---|---|---|
| GLFW error 65542 | GLFW error 65542 | What GLFW error 65542 means in Minecraft Java: how to check OpenGL, drivers, and the selected graphics card from the log without downloading DLL files from third-party sites. |
| GLFW error 65543 | GLFW error 65543 | GLFW error 65543: requested OpenGL version or profile is unavailable. Check Minecraft requirements, GPU models, active adapter, and logs. |
| Pixel format not accelerated | Pixel format not accelerated | Why does an old Minecraft version with LWJGL 2 say 'Pixel format not accelerated': check Java, hardware OpenGL, adapter, and remote session launch. |
| EXCEPTION_ACCESS_VIOLATION / -1073741819 | EXCEPTION_ACCESS_VIOLATION / -1073741819 | How to debug EXCEPTION_ACCESS_VIOLATION and error code -1073741819: find hs_err_pid, check Problematic frame, Java, and Minecraft native libraries. |
Diagnosis by symptoms
| Error | In English | What does it mean? |
|---|---|---|
| Diagnosis of black screen | Black screen | Step-by-step checks for Java, Bedrock on Windows, and Java on Android |
Error messages — directly from Minecraft 26.3 localization; causes and tips are provided in editorial notes.