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How to Read Minecraft Crash Logs

Reading logs isn’t rocket science. It’s not some mystical skill reserved for developers. At the end of the day, it’s just about paying attention to what’s in front of you.

When Minecraft crashes (whether you’re using Lunar Client, Forge, Fabric, or any other loader) the log file is your first clue to what’s going wrong. Most logs fall into two categories: mod-related ones, or system/instance related ones.

These happen when a mod you added is breaking something. Other than that, mods can also conflict with each other, which can lead to issues. In these cases, your job is to scroll until you hit the actual error. You’ll usually recognize it from patterns like:

  • [error] (or any sort prefix that indicates that this specific line is an error)
  • Caused by:
  • Critical injection failure
  • Failed to boot Minecraft

Once you spot these, keep in mind: the last relevant error before the crash is usually the one that matters. Not always, but often. Here’s a quick example:

[error] Caused by: org.spongepowered.asm.mixin.injection.throwables.InjectionError:
 Critical injection failure: Constant modifier method lunar$editFeedbackConstant
 (Ljava/lang/String;)Ljava/lang/String; in mixins.meta.lunar.modmenu.v1_21_0.json
 :IOHCRIOROICRICIICHRHCCORHROOCO from mod (unknown) failed injection check, (0/1) 
 succeeded. Scanned 1 target(s). No refMap loaded.

If you pay enough attention, it tells you:

mixins.meta.lunar.modmenu.v1_21_0.json

Translation? the modmenu mod has caused the crash.

Well, more specifically, Lunar Client tried to inject a mixin that it would inject in the presence of Mod Menu (and failed to do so). So logically, removing Mod Menu should also stop the crash.

If two mods try to modify the same thing via mixins, you’ve got a mixin conflict. That’s also a guaranteed crash. Wait, what’s a mixin?

Mixins allow mod developers to modify the game’s code without modifying it directly. Mods use mixins to inject code into the base game’s code.

From the FabricMC docs:
“Their primary use case is modifying existing code in the base game, whether it be through injecting custom logic, removing mechanics, or modifying values.”

These aren’t about mods at all. They’re about the environment the game is running in.

For these, you’re often looking for specific log lines. Once you’ve seen them a few times, you’ll recognize them instantly the next time you see them. We’ll cover two examples:

  • Outdated AMD drivers
    If you’re using an AMD graphics card and your drivers are old, Minecraft can run into issues. Depending on the launcher you use to play the game, you might be able to spot atio6axx.dll in your logs. If not, you’ll notice a log that’s almost empty. You’ll then have to look for log files inside your instance’s folder (or game directory) that are named starting with: hs_err_pid followed by some random numbers. There, you’ll find atio6axx.dll.

hs_err_pid logs indicate a Java Virtual Machine (JVM) crash. These crashes usually happen because of Minecraft running out of memory or having issues with graphics drivers.

What to do:

  • Go to AMD’s official site, download the latest drivers for your GPU, and install them.
  • If you’re on a laptop with both integrated and dedicated graphics, make sure Minecraft is actually using the dGPU (though your system’s graphics settings).
  • Corrupted game-directory files
    The game’s own files can also get corrupted, especially if you’ve been moving versions, installing mods, or had a system crash while the game was running.

What to do:

  • Close the game (and your launcher) completely.
  • Go to %appdata%
  • Rename .minecraft to .minecraft1 or anything else.
  • Relaunch the game (it will create a new .minecraft for you).
  • You can now move your worlds/packs/etc. to the new one.

Note: This solution assumes that you’re using the default game directory. If you’ve changed it in your launcher’s settings, simply set it on another directory and that’ll be it!

Final Note

When reading logs, don’t overcomplicate it. Scan for obvious errors, and learn to recognize repeated patterns for common issues. That’s it, now you know how to read crash logs!

Or do you?