Gamemode Detector

Ever wondered if the admin of that SMP you're on keeps quietly flipping into Creative or Spectator? Gamemode Detector watches every player's gamemode in the background and tells you the moment it changes - no server permissions needed, purely client-side.

What it does

Automatic chat/action bar alerts whenever a tracked player switches gamemode, including how long they were in their previous mode before switching.
/checkgamemode [player] - shows a player's current gamemode and how long they've been in it, live.
/gamemodelog [player] - shows that player's recent gamemode-switch history (oldest to newest, up to 50 by default), so you can see the full pattern, not just the latest change.
/gamemodelog help - lists all available commands.
Persistent log file - every switch, first sighting, join, and leave is written to config/gamemodedetector/gamemode-log.txt. Unlike the in-chat history, this is unbounded and survives game restarts, so it's the place to look for a full record over time.
Fully configurable via ModMenu + Cloth Config: enable/disable alerts, toggle action bar vs. chat, customize every message template with placeholders (%player%, %gamemode%, %previous%, %duration%, %time%), set how many past switches are remembered per player, and toggle file logging on/off.

What's in the log file

Each line records the date & time, whether you were in Singleplayer or Multiplayer (and if Multiplayer, the server's name/address), the player's name, and what happened:

[2026-08-08 00:14:02] [Singleplayer] 166f was already online when you connected, currently in SURVIVAL

[2026-08-08 00:20:41] [Multiplayer: MyServer (play.example.net)] Foo joined the server just now, currently in SURVIVAL

[2026-08-08 00:31:05] [Multiplayer: MyServer (play.example.net)] Foo (joined: 2026-08-08 00:20:41): SURVIVAL -> SPECTATOR (after 10m 24s)

[2026-08-08 00:45:12] [Multiplayer: MyServer (play.example.net)] Foo left the server (was in SPECTATOR for 5m 8s, joined: 2026-08-08 00:20:41)

Note: since the game protocol doesn't tell clients when someone already on the server actually joined, players present when you connect are logged as "already online" rather than given a fake join time.

How it works

Minecraft's server already tells every connected client the gamemode of all online players (that's how the tab list shows the right icon/name style for each player). Gamemode Detector simply listens to that existing data every tick, compares it to what it saw last, and reacts when something changes - it doesn't need any special permissions, plugins, or server-side installation.

This only tracks gamemode changes using data the server already broadcasts to everyone. It can't reveal players who are already hidden as Spectators when you join (vanilla intentionally hides Spectators from Survival/Adventure players at the network level) - it just tells you when a change happens from that point on.

Requirements

Fabric Loader
Fabric API
Cloth Config API
ModMenu (optional, for the in-game settings screen)

Recommended to disable in-chat alerts (or lower how it's used) on large public servers with frequent gamemode switching, to avoid chat spam.