Use the command /properties reload to reload the server.properties file (requires permission level 2 or higher). You will see a report of which properties were changed, and which are unsupported.

Supported Properties

As of 1.18, the following properties are supported:

allow-flight
allow-nether
broadcast-console-to-ops
broadcast-rcon-to-ops
difficulty
enable-command-block
enable-jmx-monitoring
enable-query
enable-rcon
enable-status
enforce-whitelist
- When enabled, it will kick non-whitelisted players even if the whitelist is disabled. This is consistent with Minecraft's existing inconsistency (for ex. /deop command will do the same).
entity-broadcast-range-percentage
force-gamemode
- Only affects players who login after the change.
- Use /defaultgamemode to set game mode for all online players.
function-permission-level
- Only takes place after reloading resource packs using /reload.
gamemode
- Only affects players who login after the change.
- Use /defaultgamemode to set game mode for all online players.
hardcore
- The heart icon and respawn menu will only update for players who login after the change, but respawning itself works as expected.
max-players
- Only affects players who try to login after the change.
max-world-size
motd
network-compression-threshold
- Only affects players who login after the change.
- When changed while a player is logging in, it might cause the connection to be setup incorrectly and cause errors. Be careful.
online-mode
- Only affects players who login after the change.
op-permission-level
- Works the same as editing server.properties and restarting, i.e. it only applies to users /op'd after the change and does not affect existing operators.
player-idle-timeout
prevent-proxy-connections
- Only affects players who login after the change.
pvp
query.port
rcon.password
- Any currently connected RCON clients will be disconnected.
rcon.port
- Any currently connected RCON clients will be disconnected.
require-resource-pack
- Only affects players who login after the change.
resource-pack
- Only affects players who login after the change.
resource-pack-prompt
- Only affects players who login after the change.
resource-pack-sha1
- Only affects players who login after the change.
simulation-distance
spawn-animals
spawn-monsters
spawn-npcs
spawn-protection
view-distance
white-list

Unsupported Properties

generate-structures
generator-settings
level-name
level-seed
level-type
max-tick-time
rate-limit
resource-pack-hash
- Use resource-pack-sha1 instead.
server-ip
server-port
snooper-enabled
sync-chunk-writes
text-filtering-config
use-native-transport

Installation

The mod only works on dedicated servers. The following mod loaders are supported:

Fabric (note: this mod does not require Fabric API)
Forge

After you install the mod loader of your choice, download the mod and place the .jar file into the mods folder of your server.