The server shows offline when I start it, or stuck starting at a % for hours — what's wrong?

Two different startup problems look similar but have different causes: a server that flips back to offline right after you start it, and one that seems stuck at a percentage. Here's how to tell them apart.

Flips back to offline

If the server goes back to offline shortly after you start it, it's crashing on boot. Open the Console and read the error — the same causes apply as any won't-start problem (wrong Java version, a bad mod/plugin, a corrupted world, or RAM).

Stuck at a percentage

1. A big modpack or world can take several minutes to generate on first boot — give it time before assuming it's stuck.
2. If it sits for hours, it's genuinely hung — usually a mod waiting on something, or it has quietly crashed.
3. Open the Console: if the log has stopped moving, restart and read the last lines for the real error.

Tip: A log that's still scrolling means the server is working, even slowly. A log frozen for many minutes is the sign that something is actually wrong.

Frequently asked questions

How long is too long at a percentage? Minutes can be normal for large modpacks on first boot. Hours is not — check whether the Console log is still moving.

It keeps flipping to offline — what do I do? That's a boot crash. Read the Console error and apply the matching fix (Java version, recent mod/plugin, world, or RAM).