Understanding Minecraft Logs

Everything lives in the logs/ folder (server root, or instance/.minecraft on a client):

• latest.log
  The current run's full log. This is the file you open first, the error is almost always here.
• debug.log
  A far more verbose version of the same run. Use it when latest.log does not say enough.
• Archived logs
  Older runs are zipped as 2026-06-08-1.log.gz. Decompress to read a past session.
• crash-reports/
  A separate folder with a focused report written only when the game crashes. See How to read a crash report.

Each line follows the same format:

[14:23:51] [Server thread/ERROR]: Encountered an unexpected exception

• [14:23:51]
  The timestamp, when the event happened.
• [Server thread/ERROR]
  The thread that logged it, and the level.
• The message
  What actually happened, often followed by a stack trace if it is an error.

The log level tells you severity at a glance: INFO (normal), WARN (something is off but not fatal), ERROR (a real failure), and FATAL (the server is going down).

• Server thread / main
  The core game loop. Errors here usually affect gameplay directly (and can crash the server).
• Worker / IO threads
  Background work such as chunk I/O. Useful for disk and world-save issues.
• Mod/plugin threads
  Named after a mod or plugin, a quick hint at what is responsible.

1. Scroll to the first ERROR/FATAL or Exception, later errors are often just consequences of it.
2. Read the startup section for failed mods/plugins, the wrong Java version, or an unaccepted EULA.
3. Watch for repeated WARN spam like "Can't keep up!" (performance, see Can't Keep Up) or "moved too quickly".
4. Note the last lines before a freeze or shutdown, they show what the server was doing when it died.
5. Cross-reference any error against the Common Issues list for the exact fix.

They share the same format but live in different places. A server log records world saving, player connections, and plugin/mod loading; a client log records rendering, resource packs, and your own connection. When troubleshooting a join problem, compare both, the cause may be on only one side.

Logs can contain your server IP and occasionally tokens, so do not paste them publicly without a glance first. Use a paste service (such as mclo.gs) for sharing, or upload the file straight into MCDoctor.ai, which reads the log and explains the cause and fix for you, no manual digging required.