Mod checker
by AVCD
Players joining a server with Mod Checker can have their installed mods compared against a whitelist or banlist kept by the server owner.
What it does
On Fabric, Mod Checker lets a server owner inspect the mod list of each connecting player. Server owners choose between two moderation modes: a whitelist mode that allows only the listed mod IDs, and a banlist mode that allows everything except the listed mods. Once configured, the check runs on its own for every join, with no manual commands needed.
Players whose mods do not match the rules are disconnected with a message. Required mods, including Mod Checker itself, can be part of the rules, and the kick text is shown in English or Russian depending on the language the player's client uses. Rules live in a modcheck.json file that is generated in the server's config folder on the first run. The environment is client and server, so the server and every player need the mod, and the source code is available under the MIT License, making it open source.
The mod is a Library, Management and Utility mod for Fabric, with files for 1.19.4 only. The latest file is 1.0.1 for 1.19.4, published on 2026-01-09.
Key features
Whitelist and banlist modes
The server can allow only listed mod IDs, or allow every mod except the listed ones.
Automatic checks on join
Each connecting player's mod list is validated against the configured rules as they join.
Custom kick messages
Disconnect messages can be edited, so players see clear reasons when a mod is missing or disallowed.
File-based configuration
Rules are set in modcheck.json, which is created in the config folder on the first run and edited by hand.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Who it’s for: Server owners running Fabric who want to control which mods players connect with. Players only need to satisfy the rules the server sets.
How it compares
Modpack Checker is open source under the Apache License 2.0, runs on client and server and covers 1.20 – 1.21.7. Slots Checker is server-side only, open source under the Apache License 2.0 and published for 1.18 – 26.3.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Mod checker | Fabric | 1.19.4 | Client and server | 2026-01-09 |
| Modpack Checker | Fabric | 1.20 – 1.21.7 | Client and server | 2025-06-30 |
| Slots Checker | Fabric | 1.18 – 26.3 | Server-side only | 2026-10-01 |
Questions
Does Mod Checker need to be installed on the client?
Where are the rules stored?
Which Minecraft version does Mod Checker support?
In the catalog
Mod checker is one of 3,514 Library mods on ModsFinder, and one of 2,348 Library mods for Fabric. 9,374 mods support Minecraft 1.19.4.
Similar mods
What the author says
Mod Checker is a server-side administration tool for Fabric/Quilt that gives server owners complete control over which mods players can use. It validates the mod list of every connecting player against a customizable whitelist or banlist, helping to maintain stability, security, and the intended gameplay experience…
Official listing
- Modrinth page
- modrinth.com/mod/mod_checker
- Owner
- AVCD
- Published
- 2026-01-08
- Updated on Modrinth
- 2026-01-09
- Facts verified
- 2026-10-15