Change or turn off spawn protection in Minecraft

The Config Editor searched for spawn, showing the Spawn protection radius row and Save.

Open the Config Editor, set Spawn protection radius in the World group to 0, choose Save and restart. That turns spawn protection off. The default is 16, which protects a square of 33 by 33 blocks around the spawn point where only operators can place or break blocks.

What it protects

Spawn protection stops players from building around the spawn point: they cannot place or break blocks there. It exists only on servers, not in singleplayer or LAN worlds, and only in the Overworld.

The number is a radius, but the area is a square. The side length is twice the number plus one:

Setting	Protected area
`0`	Off
`1`	3 by 3 blocks
`2`	5 by 5 blocks
`16` (default)	33 by 33 blocks

The square is centered on the spawn point. The Minecraft Wiki also notes that the game disables spawn protection for a negative number.

Two things do not apply:

Operators are not affected. Players in ops.json can build inside the area. See op and deop players.
A server with no operators has no protection. With nobody opped, spawn protection does not apply at all, whatever the number is.

In the ArthOS panel

Open your Minecraft server and choose Config Editor. Type “spawn” in Search (1).
In the World group, change Spawn protection radius (2). The help text reads “Blocks around spawn that only operators can change. 0 turns it off.”
Choose Save (3), then restart the server. The editor says “Saved changes apply after a restart.”

The Config Editor searched for spawn, with the Spawn protection radius row and Save — Search
Spawn protection radius
Save

The Config Editor shows the row either way.

WorldGuard can protect spawn instead. If you use it, set the radius to 0 here. See WorldGuard regions.

By hand

Open Files, then server.properties, and set:

spawn-protection=0

Save and restart. The Minecraft Wiki notes that this line is not generated on the very first start. It appears after the first player joins, so if you cannot find it yet, add the line yourself.

If it does not work

Players still cannot build near spawn. Check the value was saved and the server was restarted. A value above 0 protects a square, so players who walk a long way from the spawn point can build again.
I cannot find the setting in server.properties. It is created after the first player has joined. Add spawn-protection=0 yourself and restart.
Spawn protection does nothing for me. You are an operator, or the server has no operators. Both bypass it.
Someone breaks blocks anyway. The Minecraft Wiki lists indirect ways around spawn protection, such as pistons, dispensers, explosives and mobs that change blocks.