ModsJava
AltDetector
Java mod listed for Minecraft 1.19–1.21. Downloads from the MC Java Mods app on Android.
⬇ Download on Spigot
AltDetector
A simple, fast alt-account detector for 1.19-1.21.X — alerts staff when players share IPs.
Author: Brataas1346
✅ What is it?
A simple, fast alt-account detector for 1.19-1.21.X — alerts staff when players share IPs.
Author: Brataas1346
AltDetector checks players on join and notifies staff when the connecting player shares an IP with other accounts. Messages support & color codes, hex colors, and MiniMessage gradients so you can style alerts exactly how you want.
✨ Features
- Detects alts by shared IP on join
- Sends alerts to altdetector.notify and OPs (configurable, OPs see by default)
- Beautiful, customizable messages with & codes, hex (&#RRGGBB or <#rrggbb>), and <gradient:...>
- /alt command:
- /alt shows a clickable list of online players
- /alt <player> checks that player’s alts
- Tab-completion for online names
- /alt shows a clickable list of online players
- /altcheck <player> — check any player in the datastore
- Name preview limit (e.g. "User1, User2 (+3 more)")
- Privacy option: store real IPs or SHA-256 hashed keys
- Exempt trusted users from checks/storage
- Console also receives alerts
Requirements
- Java 21
- Minecraft server 1.21.11 (built against Paper API; works on modern Paper/Spigot with Adventure)
- Drop the jar in plugins/
- Start the server once to generate config/data
- (Optional) Edit plugins/AltDetector/config.yml to customize messages and behavior
- Grant staff the permissions below
Code (Text):
/alt - Clickable list of online players to check
/alt <player> - Check a specific player's alts
Permissions
| Permission | Description | Default | |
| altdetector.notify | See alt alerts on player join | op | |
| altdetector.use | Use /alt to check players | op | op |
| altdetector.exempt | Player is exempt from detection & storage | false |
Note: OPs always see alerts by default (configurable via ops-always-see).
⚙️ Configuration
Spoiler: config.yml (defaults)
notify-permission : "altdetector.notify"
ops-always-see : true
min-matches : 1
name-preview-limit : 5
# Placeholders: {player}, {ip}, {matches}, {count}
alert-format : "<gradient:#ff6a00:#ffd800>[AltDetector]</gradient> &e{player} &7shares IP with &c{matches} &7(&f{ip}&7)"
no-matches-format : "<gradient:#6a86ff:#b86bff>[AltDetector]</gradient> &aNo matches for &e{player}&a."
# Store real IPs (true) or SHA-256 hashed keys (false)
store-plain-ip : true
Placeholders
Code (YAML):
notify-permission : "altdetector.notify"
ops-always-see : true
min-matches : 1
name-preview-limit : 5
# Placeholders: {player}, {ip}, {matches}, {count}
alert-format : "<gradient:#ff6a00:#ffd800>[AltDetector]</gradient> &e{player} &7shares IP with &c{matches} &7(&f{ip}&7)"
no-matches-format : "<gradient:#6a86ff:#b86bff>[AltDetector]</gradient> &aNo matches for &e{player}&a."
# Store real IPs (true) or SHA-256 hashed keys (false)
store-plain-ip : true
- {player} – the player being checked
- {ip} – the stored IP or hashed key
- {matches} – comma-separated preview of matched names
- {count} – total number of matching names (excluding {player})
- & codes: e.g. &6&lGold Bold
- Hex: &#FFAA00 or <#ffaa00>
- Gradients: <gradient:#ff6a00:#ffd800>Your Text</gradient>
Code (Text):
/alt
# -> clickable list of online players; click a name to run /alt <name>
/alt Silver
# -> shows "Brataas1346 shares IP with Name1, Name2 (+2 more) (1.2.3.4)"
Privacy
- Set store-plain-ip: false to store only a SHA-256 hash key and show that in alerts
- Grant altdetector.exempt to trusted players/accounts to skip storage and alerts
Changelog
- 1.0.0 — Initial release: join alerts, /alt with clickable list & tab-complete, /altdetector reload & lookup, styled messages (&, hex, gradients), IP hashing option, exemptions.
Quick facts
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.19, 1.20, 1.20.6
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on Spigot — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — How to install Minecraft Java mods & modpacks walks through it step by step.
AltDetector is a free Minecraft Java mod. Compatible with Minecraft 1.19, 1.20, 1.20.6, 1.21. Downloaded 97 times (via Spigot). Download it and open it directly in the game.