horizon/docs/api/server-reference.md

Server reference

Everything horizon-server offers a host or a tool: its commands, every server.toml key and the control API. How to host: hosting.md; the design: server.md; stability and versions: stability.md.

Commands

horizon-server help prints:

horizon-server: host a Horizon (Minecraft Java Edition 26.3) server

Usage: horizon-server [--dir DIR] <command>

  init        Set up a server here: the EULA, the world, the port, who may join (asks, or takes flags:
              --eula --world NAME --seed SEED --port N --whitelist/--no-whitelist --player NAME... --op NAME
              --offline --yes)
  run         Run the server in the foreground; type console commands, Ctrl-C stops it cleanly. It
              restarts the game if it crashes.
  start       Run the server in the background, or resume a stopped supervisor (output goes to logs/supervisor.log)
  stop, restart
  status [--json]
              Up or not, TPS, MSPT, players, RAM and CPU
  cmd COMMAND...
              Run a console command on the running server and print what it answers
  report [SECONDS]
              Record a performance report for SECONDS (default 60): where the ticks' time goes,
              entities, chunks, network, memory; saved in reports/ (JSON and text, no player data)
  logs [-f] [-n N]
              The last N lines of the log (default 50); -f follows it
  console     Attach to the running server: its log as it happens, TPS, MSPT, players and RAM at the
              top, and a command line for console commands; Ctrl-D detaches
  mcp         An MCP server on stdin and stdout, for an AI agent to run and moderate the server
              (players, kick, ban, whitelist, logs, events, backups, settings, restart...)
  backup [NAME]
              Zip the world and the settings into backups/ (a running server saves first and stays up)
  backups [--json]
              List the backups
  restore BACKUP [--dimension ID] [--yes]
              Put a backup's world in place (the current one is kept in backups/); a running
              server restarts with it. --dimension (like minecraft:the_nether) brings back only
              that dimension and leaves the rest of the world as it is
  service install|uninstall|print [--system]
              Start the server at boot or login: a systemd unit on Linux (--system: for every user,
              with sudo), a launchd agent on macOS, a task at logon on Windows
  panel       A one-time login link for the web panel ([panel] in server.toml; 127.0.0.1:8130 by
              default)
  update [--check [--json]] [--version TAG] [--timeout SECONDS]
              Install the newest release (checked against GitHub's SHA-256), back up the world and
              restart on it; goes back by itself if the game isn't up within the timeout (300 s).
              --archive FILE --version NAME installs an archive you have
  rollback    Back to the release used before the update
  config [--json]
              The settings in server.toml
  config set KEY=VALUE... [--json]
              Change settings (for example world.difficulty=hard server.max_players=10), checked first;
              a running server takes the difficulty, default game mode and whitelist at once, the rest
              at its next start
  import FILE Write server.toml from a vanilla server.properties
  import-resources DIR
              Copy game files prepared elsewhere (by the launcher or horizon-prepare) into place, after
              checking they are complete and for this Minecraft version; the old copy stays on failure
  op NAME, deop NAME
  whitelist on|off|list, whitelist add|remove NAME
              Who may join (on the running server, or in the files when it is stopped)
  players [--json]
              Who is online, the operators, the whitelist and the bans
  kick NAME [REASON], ban NAME [REASON], pardon NAME, ban-ip ADDRESS|NAME [REASON], pardon-ip ADDRESS
              Moderate the running server, or edit ban files while it is stopped

  --dir DIR   The server folder (default: the current folder)

Settings live in server.toml; the server writes server.properties from it before every start.

server.toml

Horizon server settings (docs/server.md). The server writes them into server.properties before every start: edit this file, not that one. Unknown keys are refused. horizon-server init writes this file with these defaults; horizon-server config set SECTION.KEY=VALUE changes it.

[server]

Key	Default	In server.properties	What it does
motd	"A Minecraft Server"	motd	the line under the server's name in the server list
port	25565	server-port	the port players connect to
bind	""	server-ip	listen on every address, or only on this one (server-ip)
max_players	20	max-players	how many players can be online at once
online_mode	true	online-mode	check players' Minecraft accounts (false: anyone joins under any name)
whitelist	true	white-list	only whitelisted players and operators can join
enforce_whitelist	false	enforce-whitelist	kick online players taken off the whitelist
view_distance	10	view-distance	chunks sent around each player
simulation_distance	10	simulation-distance	chunks around each player where mobs, crops and redstone tick
max_view_distance	0	horizon-max-view-distance	past view_distance, saved chunks only, up to this (never generated; 0: off)
admin_feedback_to_ops	true	horizon-admin-feedback-to-ops	operators see each other's commands ([name: ...], vanilla); false: only the log
accept_older_clients	false	horizon-accept-older-clients	true: 26.2 clients join too, their packets translated (docs/hosting.md)

[world]

Key	Default	In server.properties	What it does
name	"world"	level-name	the world folder
seed	""	level-seed	empty: a random seed on the first start
game_mode	"survival"	gamemode	survival, creative, adventure or spectator
difficulty	"easy"	difficulty	peaceful, easy, normal or hard
hardcore	false	hardcore	one life: a player who dies becomes a spectator

[properties]

Any other server.properties key, spelled as vanilla spells it, for example: spawn-protection = 16

[engine]

Key	Default	In server.properties	What it does
path	""		the game program; empty: the one installed beside horizon-server
resources	""		the prepared game files; empty: resources/ here, else the usual places
restart_on_crash	true		start the game again when it crashes
low_memory	false		true: no transparent huge pages, ~60 MB less idle for ~1 % more tick time

[backups]

Key	Default	In server.properties	What it does
every	"6h"		automatic backups while the server runs: 30m, 6h, 1d...; "0" turns them off
keep	12		automatic backups kept (backups made by hand are never deleted)

[updates]

Key	Default	In server.properties	What it does
keep	1		other releases kept by updates, besides the one in use and the one rollback goes to

[panel]

Key	Default	In server.properties	What it does
bind	"127.0.0.1:8130"		the web panel: this computer only, or a tailnet address (100.x); "" turns it off
allow_public	false		true lets bind be any address; never put the panel on the open internet

[api]

Key	Default	In server.properties	What it does
bind	""		the control API: "" a free port on 127.0.0.1; or a fixed one, like 127.0.0.1:8131 or a tailnet address
token	""		its token (16 characters or more); "" a new random one at every start
allow_public	false		true lets bind be any address; the token is then all that guards the server

[transfer]

A proxy handing players over between servers (docs/server.md). Not vanilla's accepts-transfers (the transfer packet).

Key	Default	In server.properties	What it does
enabled	false		true: take a proxy's player-* requests; needs Velocity forwarding (forwarding.secret)
expect_seconds	10		how long a player the proxy announced is waited for, when it names no time
max_expect_seconds	60		the longest the proxy may ask for
max_expected	64		players waited for at once
max_freeze_seconds	30		the longest a player stays frozen while it is handed over
max_hold_seconds	60		the longest a player arriving from another server is held before it is dropped

[discord]

Post the chat, joins, leaves and deaths to a Discord channel, drawn like the in-game chat (docs/hosting.md)

Key	Default	In server.properties	What it does
webhook	""		the channel's webhook URL (a secret: anyone with it can post there); "" off
events	["chat", "join", "leave", "death"]		what is posted; "kick" too if you like
enabled	true		false pauses it and keeps the webhook

Control API (/api/v1)

HTTP and JSON on 127.0.0.1. A running server writes its address and a random token to .horizon/api.json, readable only by its own user; every request sends Authorization: Bearer <token> and a Host that is that address. Errors answer {"error": "..."} with 400, 401, 403, 404, 405 or 409. The web panel uses the same routes with its session.

Method	Path	Takes	Answers	What it does
GET	/api/v1/status	nothing	phase, version, pid, uptime_seconds, engine_pid, engine_uptime_seconds, crashes, last_crash, sample (TPS, MSPT, players, RAM, CPU), update	How the server does
GET	/api/v1/metrics	?since=T (seconds since 1970)	{"samples": [...]}: one a second, the last 10 minutes	The samples taken after T, for graphs
GET	/api/v1/logs	?since=N	{"next": N, "lines": [...]}	The log lines after the Nth (the last 2000 are kept)
GET	/api/v1/events	?since=N (or Last-Event-ID), ?types=join,leave,kick,chat,chat_filtered,death,log,phase (all by default)	with Accept: text/event-stream, server-sent events as they happen (id, event: the type, data: JSON); otherwise {"next": N, "events": [...]}	Log lines, the supervisor's phase, and the game's joins, leaves, kicks, chat, messages the chat filter refused (chat_filtered, without their text) and deaths (the last 2000 kept)
POST	/api/v1/command	{"line": "<one command>"}	the lines the command logged	Run a console command on the running game
POST	/api/v1/stop	nothing	{"ok": true}	Stop the game and the supervisor
POST	/api/v1/start	nothing	{"ok": true}	Start the game while keeping the supervisor and API running
POST	/api/v1/restart	nothing	{"ok": true}	Restart the game
GET	/api/v1/backups	nothing	{"backups": [{"name", "bytes"}]}	List the backups
POST	/api/v1/backups	{"name": "..."} (optional)	{"name": "<file>"}	Back up now (a running game saves first and stays up)
DELETE	/api/v1/backups	?name=<file> (the full name backups lists)	{"name": "<file>"}	Delete a backup
GET	/api/v1/backups/download	?name=<file>	the zip	Download a backup
GET	/api/v1/crash-reports	nothing	{"reports": [{"name", "bytes"}]}, newest first (the .txt files in crash-reports/)	List the game's crash reports
GET	/api/v1/crash-reports/read	?name=<file> (a name crash-reports lists)	the report's text (text/plain)	Read one crash report
POST	/api/v1/restore	{"name": "<backup>", "dimension": "minecraft:the_nether"} (dimension optional)	{"name": "<backup>", "dimension": "<id>" or null}	Restart the game with that backup's world, or only one dimension of it (what it replaces is kept in backups/)
POST	/api/v1/update	{"tag": "...", "timeout": seconds} (both optional)	{"ok": true}; status says how it went (update)	Restart on that installed release, or download the newest first; goes back if the game isn't up within the timeout
GET	/api/v1/metrics/prometheus	nothing	the latest sample as Prometheus text: horizon_up, horizon_tps, horizon_mspt{stat}, horizon_players_online, horizon_memory_rss_bytes, horizon_loaded_chunks{dimension} and horizon_entities{dimension} (players and block entities apart)...	Metrics for a monitoring tool to scrape
GET	/api/v1/players	nothing	online (name, uuid, address, ping_ms, dimension, position, op_level), max_players, ops, whitelist (enabled, players), bans, ip_bans (with reason, source, created, expires)	Who is online, and vanilla's lists
GET	/api/v1/mods	nothing	engine (found, target, base, horizon, hooks) and native (id, version, sha256), from the native-mods.json the launcher wrote beside the game program	The native mods the server's game program was built with
POST	/api/v1/players/kick	{"name", "reason"} (reason optional)	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Kick an online player
POST	/api/v1/players/ban	{"name", "reason"} (reason optional)	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Ban a player (kicked if online)
POST	/api/v1/players/pardon	{"name"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Lift a player's ban
POST	/api/v1/players/ban-ip	{"ip", "reason"}, or {"name"} of an online player	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Ban an address (its players are kicked)
POST	/api/v1/players/pardon-ip	{"ip"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Lift an address's ban
POST	/api/v1/players/op	{"name"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Make a player an operator (op-permission-level)
POST	/api/v1/players/deop	{"name"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Make a player no longer an operator
POST	/api/v1/whitelist	{"enabled": bool}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Turn the whitelist on or off
POST	/api/v1/whitelist/add	{"name"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Whitelist a player
POST	/api/v1/whitelist/remove	{"name"}	{"changed": bool, "output": [...]}: whether the list (or who is online) changed, and the console's lines	Take a player off the whitelist (kicked if enforce-whitelist)
GET	/api/v1/config	nothing	{"config": {...}}: server.toml's settings by section (api.token hidden)	The settings
PATCH	/api/v1/config	{"changes": {"world.difficulty": "hard", ...}}	saved, applied (taken by the running game at once), restart (from the next start), running	Change settings as config set does; not engine.*, panel.*, api.*, nor RCON, query or management keys
POST	/api/v1/panel/login	nothing	{"url": "..."}	A one-time login link for the web panel (with the token only, not from the panel)