ModBlocker

A BepInEx 5 preloader patcher for Valheim (and other BepInEx games) that prevents blocklisted mods from loading — without uninstalling them.

Why?

Modpack maintainers have no way to remove a mod from players' machines: updating a modpack installs new dependencies but never uninstalls dropped ones. ModBlocker fixes that. Ship it in your modpack with its config file, and removing a mod for every player becomes a one-line config change in your next pack update.

How it works

At game startup — before the BepInEx chainloader scans plugins — ModBlocker reads BepInEx/config/modblocker.cfg and renames the DLLs of blocklisted mods to .dll.blocked. Blocked mods simply do not exist as far as the game is concerned. Removing an entry restores the DLLs on the next launch. Nothing is ever deleted.

Config: BepInEx/config/modblocker.cfg

Comma-separated entries. Two formats are supported, matching is case-insensitive:

[Blocklist]
Mods = SomeAuthor-SomeMod, SomeOldPlugin.dll

Editing in-game

The companion plugin ModBlockerUI exposes the blocklist as a text field in the ConfigurationManager window (F1). Changes are saved instantly and applied on the next launch (blocking happens before plugins load, by design).

A log of every block/re-enable action is written to BepInEx/ModBlocker.log.

Server enforcement (v1.3+)

Install ModBlocker on the server (or in-game host) and on all clients:

• The server's blocklist is pushed to every connecting client (ServerSync, Lock Configuration = true) and applies on their next launch.
• Players without ModBlocker installed are kicked on connect (ModRequired), like AzuAntiCheat does for its whitelist.
• Server values never overwrite the client's local modblocker.cfg; they are mirrored to modblocker.server and merged by the preloader at startup.

ServerSync is embedded from blaxxun's ServerSync — all credit to blaxxun.

Safety nets

• Core protection: BepInEx and Jotunn can never be blocked — entries targeting them are refused and logged.
• Cascade blocking: if you block a mod that other mods depend on, those dependents are automatically blocked too, recursively (2, 3, 5 mods — the whole chain). Each cascade is logged as Also blocked: X (depends on Y). Removing the original entry restores the entire chain on the next launch.
• Self-protection: entries targeting ModBlocker's own components are ignored.

Warnings

• Blocking a mod that others depend on blocks the dependents as well (see cascade above) — check BepInEx/ModBlocker.log to see the full chain.
• Blocking a content mod (items/creatures) has the same effect on an existing world as uninstalling it: its objects will be missing while blocked.

Building from source

cd src
dotnet build -c Release

Patcher: dotnet build src → src/bin/Release/net472/ModBlocker.dll → BepInEx/patchers/ Plugin: dotnet build src/Plugin → src/Plugin/bin/Release/net472/ModBlockerUI.dll → BepInEx/plugins/

FAQ

Does blocking delete anything? No. DLLs are renamed to .blocked, never deleted. Remove the entry and they are restored on the next launch.

Can it block itself? No — entries targeting ModBlocker's own components are ignored and logged.

Does it work outside Valheim? It should work with any BepInEx 5 game, but it is only tested on Valheim.

Contributing

Issues and pull requests are welcome. The CI builds both DLLs and assembles the ready-to-upload Thunderstore package on every push (see Actions artifacts). Pushing a vX.Y.Z tag creates a GitHub Release with the package attached.

License

MIT — © 2026 Ashraf