A Minecraft world can represent months of builds, inventories and shared memories. Copying a folder occasionally is better than nothing, but a recovery plan needs one more step: prove the copy works.
Before a version upgrade, a modpack change or a major plugin installation, take a complete backup you can actually recover.
Back up the full server, and test a restore.
Save the world directories plus server configuration, plugin or mod data, and any external databases used by plugins. Stop the server or use a backup method that provides a consistent snapshot. Keep an off-server copy and restore it to a test server before relying on it.
Minecraft Java Edition server administrationA world folder is not always the entire server
World data is the obvious priority, including the Overworld and any Nether or End folders used by your server software. Plugin data can contain claims, permissions, economy balances and player settings that will not come back with terrain alone.
Also keep configuration such as server.properties, whitelist and operator files, startup settings, mod and plugin versions, and any external database dumps. Check your software's folder layout before deciding which directories can be excluded.
Make sure the files agree with each other
The safest simple method is to stop the server, copy its data and restart it. For online backups, use a supported snapshot or backup process that flushes pending writes and captures database state consistently. A live file copy without a consistency strategy can preserve partially updated data.
Timestamp each backup, note the game version, and store it somewhere outside the server node. A backup saved only on the same disk may disappear with the original.
Do one restore before calling the job finished
Create an isolated test server using matching software versions. Restore the files, start it and check the spawn, inventories, dimensions, plugin data and representative builds.
If a world or plugin fails to load, keep the original untouched while you investigate. Test restores again after major updates because procedures and file layouts can change.
Set a schedule that matches the value of your world
An active community may need daily backups and additional snapshots before major changes. Keep several generations rather than replacing yesterday's only good copy with today's broken one.
Limit who can delete backup copies, and periodically check storage capacity and failed jobs. A notification that a backup failed is far more useful than learning about it during an outage.
A couple more questions
Can I just copy the world folder while people are playing?
It may work, but it risks inconsistent files if saves occur during the copy. Prefer a stop-and-copy process or documented consistent snapshot workflow.
Do backups also preserve plugin databases?
Only if you explicitly include their data. Plugins using an external database need a compatible database backup as well.
Sources & useful links
The technical details behind this guide, if you want to dig further.