Mod Access Control

Mod Access Control

A server-side Minecraft mod that gives server owners precise control over
which mods players may (or must not) have installed. It behaves identically on
Forge, Fabric, and NeoForge, with one shared config file and the
same /mac command suite.

Note: Clients must also install this mod to complete the handshake.
Clients without it are denied on join (configurable via requireClientMod).

Features

• Two-stage handshake — a lightweight protocol/loader exchange at login,
  full mod-list verification before entering the world, then periodic re-checks
  using the reported list (no repeated transfers).
• Required-mod checks — enforce presence (presence), version ranges
  (version_range), or strict matching (strict).
• Policy system — whitelist, blacklist, or switch (dual-mode with a
  hot-swappable active policy and interval re-checks).
• In-game rule management — view, edit, reload, and save
  whitelist/blacklist/required lists live via /mac commands, with
  tab-completion and one-click list building from any player’s mods
  (/mac learn).
• Multi-language, server-side — all messages (kick screens, admin alerts,
  command feedback) follow the server’s configured language:
  zh_cn, zh_tw, en_us, ja_jp, ru_ru (/mac lang <language>, keys are
  shipped as JSON catalogs and easy to extend).
• Clear player feedback — the disconnect screen lists exactly which required
  mods are missing, which versions mismatch, and which banned/off-list mods
  were found, plus a customizable footer hint area.
• Exemptions — skip all checks for specific players (name or UUID) or all
  OPs.
• Dry-run mode — detect and log violations without kicking, so you can
  validate rules before going live.
• Mod history & audit — every player’s mod list is persisted (JSONL) and
  auditable via /mac audit / /mac recent.
• Admin alerts — online admins get chat + action-bar + sound notifications
  on every block.
• Robust error handling — corrupted configs are auto-backed up and reset;
  failures are caught and logged, never crashing the server.

Configuration

File: <server>/config/mod_access_control.json (auto-generated on first start)

Key options:

• enabled — master switch
• requireClientMod — require the client mod (default true)
• strictLoader — require a matching mod loader
• requiredCheckMode — presence / version_range / strict
• policy.mode — whitelist / blacklist / switch
• language — server message language: zh_cn / zh_tw / en_us / ja_jp / ru_ru
• exemptPlayers / exemptOps — exemptions
• dryRun — log violations without kicking
• allowedMacVersions — restrict which versions of this mod may connect

Commands

/mac — status, recent, check, audit, learn, reload, save,
recheck, enabled, dryrun, mode, active, exempt, allowedmac,
required, whitelist, blacklist, and lang.
Run /mac help in-game for the full list.