Mismatched mod channel list, missing registry entries and other mod errors

Errors such as Mismatched mod channel list, Fatally missing registry entries, Failed to synchronize registry data or Incomplete set of tags received from server. Please contact server operator. all mean the same thing: the mods on the player's game are not the same as the mods on the server. Modded Minecraft needs both sides to match closely.

Why it happens

• The player is missing a mod the server has (or has an extra one that must also be on the server).

• A mod has a different version on the player's game and the server.

• The mod loader is different: Forge vs NeoForge vs Fabric, or a different loader version.

• The modpack version is different, for example the server was updated but players still have the old pack.

• The player is trying to join with a plain (unmodded) game.

How to fix it

1. Read the list in the error. NeoForge and newer Forge versions often show which mod or channel is missing or mismatched. Fabric errors usually name the mod or registry. The server's logs/latest.log may say more: see How to read logs.

2. Using a modpack? Have every player install the same modpack and the same pack version as the server, using CurseForge, Modrinth, Prism or the pack's own launcher. This is the easiest way to keep everything matched. If you installed the pack from the Modpacks tab, check which pack version you picked there and give players that exact version.

3. Using your own mod list? Compare the server's mods folder (in Files, or Mods → Manage Mods) with the player's mods folder. Make the file names and versions match. Players may also have client-only mods (minimaps, shaders, performance mods) that the server doesn't need; those are normally fine.

4. Match the loader. The server's software and version are shown at the top of the Versions tab. The player must use the same loader and the same Minecraft version, ideally the same loader version too.

5. Restart and try again. After changing server mods, restart the server before testing.

Server-side only and client-side only mods

• Some mods only run on the server (for example many admin or performance mods). Players don't need them.

• Some mods only run on the player's game (shaders, minimaps, zoom). They must not be on the server, or it may fail to start. See Server won't start.

• Mods that add content (blocks, items, mobs, dimensions) must be on both, with the same version.

Frequently asked questions