Sentinel&ModGuard
by Treamhiler
Sentinel&ModGuard is a Fabric client mod that answers a server's encrypted mod check, so players can join servers that screen installed mods.
What it does
On connection, a ModGuard server plugin sends the player an encrypted challenge. The Sentinel client mod receives it, collects the full mod list through FabricLoader, encrypts the list and returns it. The plugin then checks the reply against a blacklist of mod IDs and can enforce a minimum Sentinel version or a cap on the total number of installed mods.
The cryptography relies on three layers. An RSA-2048 keypair is generated anew for each server session and kept only in memory. Ciphertext is protected by authenticated encryption with a 256-bit AES key in GCM mode, so any tampering is detected. Payloads carry an HMAC-SHA256 signature made with a server secret that is never sent to the client, and each challenge includes a nonce against replay attacks.
Server owners can add or remove mod IDs from the list, configure kick messages, keep a persistent player whitelist, and allow cracked servers. Geyser and Floodgate connections bypass the check automatically. The server plugin is published for Paper and Spigot.
Key features
Encrypted mod list check
The client returns its full mod list in an encrypted reply that the server verifies before admitting the player.
Blacklist enforcement
Mod IDs on the server's blacklist are matched against each player's installed mods and blocked on a hit.
Version and mod count limits
A minimum Sentinel version can be required, and the total number of installed mods can be capped.
Whitelist and kick messages
A persistent player whitelist and configurable kick messages control who passes the check and what they see.
Gallery
Compatibility
Latest build for each game version and loader.
1.21.x11 of 11 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Who it’s for: Server owners who want to control which mods connecting players run. The mod is a client mod for players and a plugin for the server, so both sides need installing.
How it compares
Packet Sentinel is a Fabric client mod for 1.21 – 1.21.11 with the same client-only environment, released under All rights reserved and not open source. Hidder is a Fabric option for 1.21.4 – 26.1.1 that runs on client and server and is open source under the GNU Affero General Public License v3.0 or later. SerendiModGuarder is also client and server, for 1.20.6 – 26.3, and is open source under the GNU General Public License v3.0 only.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Sentinel&ModGuard | Fabric | 1.21 – 1.21.11 | Client-side only | 2026-03-08 |
| Packet Sentinel | Fabric | 1.21 – 1.21.11 | Client-side only | 2026-03-23 |
| Hidder | Fabric | 1.21.4 – 26.1.1 | Client and server | 2026-04-05 |
| SerendiModGuarder | Fabric | 1.20.6 – 26.3 | Client and server | 2026-10-04 |
Questions
Does Sentinel&ModGuard need to be installed on the server?
Which game versions does Sentinel&ModGuard support?
How is a player installed the mod?
In the catalog
Sentinel&ModGuard is one of 8,016 Management mods on ModsFinder, and one of 5,930 Management mods for Fabric. 19,862 mods support Minecraft 1.21.11.
Similar mods
What the author says
🔌 ModGuard — Server Plugin Sends encrypted challenges to connecting players, verifies responses, checks mod IDs against a blacklist, enforces a minimum Sentinel version, and optionally limits total installed mods. Supports cracked servers, Geyser/Floodgate auto-bypass, configurable kick messages, player whitelist…
Official listing
- Modrinth page
- modrinth.com/mod/sentinel-for-modguard
- Owner
- Treamhiler
- Published
- 2026-03-08
- Updated on Modrinth
- 2026-03-08
- Facts verified
- 2026-10-15