Nearly every plugin config is YAML, and YAML decides what belongs to what purely from indentation. One space in the wrong place turns a working file into one the server refuses to read.
The rules that cause the problems
- Spaces only. A tab character anywhere in a YAML file is a syntax error, and most editors insert tabs by default.
- Indentation is meaning. Two spaces deeper means «inside the thing above me».
- A value with a colon in it needs quotes:
message: "Time: 5s", notmessage: Time: 5s. yes,no,onandoffare read as true and false. If you want the word, quote it.- Colour codes starting with
&are fine, but a value starting with&alone is an anchor. Quote those too.
Editing safely
- Copy the file before you touch it
In the file manager, duplicate
config.ymltoconfig.yml.bak. Thirty seconds of insurance against an hour of guessing what you changed. - Change one thing at a time
Five edits at once means five suspects when it breaks. One edit, restart, check — it feels slower and is not.
- Restart, do not reload
Configs are read at startup.
reloadmostly works and occasionally leaves the plugin in a state nobody can debug. - Check the console on the way up
A YAML error names the line. It is usually one or two lines above where it says, because that is where the structure actually broke.
The server holds its own copy in memory and writes it back on shutdown. Editing server.properties or a plugin's config on a running server means your change gets overwritten when it stops. Stop first, edit, then start.
If the console complains and you cannot see why, an online YAML checker points at the exact character. It is faster than staring, and it teaches you the pattern for next time.
The server starts with no config errors in the console, and the setting you changed behaves differently in game.