Logs and crash reports: how to read them
Where Millida server logs are stored, how WARN differs from ERROR, how to find the culprit plugin in a stack trace, and how to interpret common console lines.
更新日 2026年8月4日
The log answers almost any “why” question, if you know where to look. The skill pays off from the very first crash.
Where to look
- “Console” — live output right now, with history and search.
logs/latest.login Files — the same log in full. Previous runs sit next to it in.log.gzarchives.crash-reports/— separate files that appear only when Java itself crashes (usually on modpacks).
What a line is made of
[12:03:44] [Server thread/ERROR]: [Essentials] Error in config
Time → thread → level → source in square brackets → text.
| Level | Should you react |
|---|---|
INFO | no, normal server life |
WARN | sometimes: the server coped, but something is off |
ERROR | yes, something failed |
FATAL | the server is dying right now |
A pile of WARN at startup on modpacks is normal. Focus on the first ERROR, not the last one: what follows is usually fallout.
Find the culprit in a stack trace
A stack trace is a long strip of lines starting with at …. You don't need to read all of it:
- The top line after
Caused by:— what exactly broke. - Look for a familiar name in the
atlines —at com.plugin.name…. That's your culprit. Exception in thread "main"at startup is a core or Java problem, not a plugin.
A line like [Plugin] Enabling Plugin v1.2 right before the error is a hint too: it crashed while enabling that specific plugin.
Common lines
| Line | What it means |
|---|---|
Can't keep up! Is the server overloaded? | the server can't keep up with ticks — Lag and TPS |
java.lang.OutOfMemoryError | the plan's memory ran out |
A single server tick took 60.00 seconds (watchdog) | something blocked the main thread — almost always a plugin or mod |
UnsupportedClassVersionError | the .jar was built for a newer Java — Core and version |
Server attempted to load chunk saved with newer version | the world is newer than the server version |
while scanning a simple key | broken YAML config: tabs or indentation |
Failed to load level | the world is corrupted — restore a backup |
Invalid signature for profile public key | 1.19+ chat signature; have the player reconnect |
Unable to access jarfile | the core file is missing — restore the core from the catalog |
Address already in use | the port is taken by a previous process; restart the server from the control panel |
What to send to support
Not a screenshot of the last line, but a chunk of the log from startup to the error — or a link to the file. Ideally: the whole latest.log plus a description of “what you did before it happened”. That way you get an answer in minutes.
Modpacks
On Forge and Fabric, also check crash-reports/crash-*.txt: at the top there's a -- Head -- block with the exact cause, and a list of mods at the bottom. The Missing or unsupported mandatory dependencies error means a mod needs another mod — install the dependency.
