Modpack Checker
by TriibuNupsik
Modpack Checker makes a Minecraft server verify that each joining client runs the expected modpack version, by comparing a version string during login.
What it does
During login the server sends a version check to the connecting client, and the client replies with the version recorded in its modpack-checker-client.toml file. The server then compares that reply with the version it expects. A mismatch leads to an automatic disconnect with a message that explains the problem, so players learn why they cannot join.
The mod is a lightweight Fabric mod that depends on Fabric API. A server running it needs every connecting player to have it too. Both sides are configured through simple TOML files, and the code is open source under the Apache License 2.0. Files cover 1.20 – 1.21.7, with 0.1.2+1.21.x for 1.21.7 as the latest build, published on 2025-06-30.
Key features
Version-based login check
The server asks each client for its modpack version during login and compares the answer with the expected value.
Automatic disconnect
A client with a mismatched version is removed from the server, and the disconnect screen states the reason.
Editable TOML configuration
Both the client and the server read TOML config files that can be edited by hand.
Gallery
Compatibility
Latest build for each game version and loader.
1.21.x8 of 8 versions with builds
1.20.x7 of 7 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Use cases
Private modpack servers
Server owners distributing a fixed modpack can make sure only players with the matching build can connect.
Pack updates
After a new pack release, the expected version on the server is changed so outdated clients are turned away with a clear message.
Who it’s for: Server owners who distribute a modpack and want to block players running a different build. Pack developers can use development mode while testing.
How it compares
Poime's Mod Checker is a Fabric mod for 1.21.4 under the MIT License, and it runs on client and server like Modpack Checker. Simple Update Checker covers Fabric and Quilt for 1.21.1 – 26.3, is optional on either side, and is released under the GNU Lesser General Public License v3.0 only. Simple Modpack Update Checker is client-side only for 1.21 – 26.3 under the MIT License, so it does not check the server's expectations.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Modpack Checker | Fabric | 1.20 – 1.21.7 | Client and server | 2025-06-30 |
| Poime's Mod Checker | Fabric | 1.21.4 | Client and server | 2025-05-26 |
| Simple Update Checker | Fabric and Quilt | 1.21.1 – 26.3 | Client or server, optional | 2026-09-11 |
| Simple Modpack Update Checker | Fabric | 1.21 – 26.3 | Client-side only | 2026-09-03 |
Questions
Does Modpack Checker need Fabric API?
Does Modpack Checker have to be installed on both sides?
How can the checks be turned off during development?
In the catalog
Modpack Checker is one of 8,016 Management mods on ModsFinder, and one of 5,930 Management mods for Fabric. 13,697 mods support Minecraft 1.21.7.
More from TriibuNupsik
Similar mods
What the author says
A lightweight Fabric mod to verify that players use the correct modpack version on your server.
Official listing
- Modrinth page
- modrinth.com/mod/modpack-checker
- Owner
- TriibuNupsik
- Published
- 2025-06-30
- Updated on Modrinth
- 2025-06-30
- Facts verified
- 2026-10-15