Fix the mismatched mod channel list error

A player tries to join your modded server and is thrown out with "Connection closed - mismatched mod channel list", or sees a screen that lists mods with columns headed "You need", "You have" and "Server has". It means the player's mods and your server's mods do not agree. The fix is to make both sides run the same loader and the same mod files.

Checked against the Forge 1.20.1 and 26.3 source, Forge language files from 1.18 to 1.21.11 and the NeoForge 1.21 language file, October 2026. This error belongs to Forge and NeoForge.

What the message means

Forge and NeoForge mods can open network channels, and each channel carries a version. When a player joins, the client and the server compare their channel lists. If a channel is missing on one side or the two versions disagree, the server or the client ends the connection. In Forge's code the text it sends is "Connection closed - mismatched mod channel list".

What the player sees depends on the version:

• Older Forge (1.16 and similar) disconnects the player with that line.
• Newer Forge (checked on 1.20.1, 1.20.4, 1.21.11 and 26.3) also opens a screen. It says "Your client is missing the following mods, install these mods to join this server", or "The server is missing the following mods, remove these mods from your client to join this server", or "The following mod versions do not match, install the same version of these mods that the server has to join this server". A table underneath lists the mod name, what you need, what you have and what the server has.
• NeoForge names the channel instead: Channel of mod "<name>" failed to connect, followed by a reason such as "This channel is missing on the server side, but required on the client!".

The server list can warn before anyone joins. Forge shows "Server mod list is not compatible" when the player has mods the server lacks, "Server has additional mods that may be needed on the client" when the server has extras, and "Server network message list is not compatible" when the channels differ.

Find what differs

1. Open the server's Console and look at the lines around the player's join. On Forge 1.20.1 the server logs Channels [...] rejected their client side version number with the channel names, then Terminating connection with client, mismatched mod list. Press Download Log if you need the whole file.
2. Open the File Manager, go into mods, and note the file names. Most carry a version number.
3. Ask the player to open the mods folder in their game folder (%appdata%\.minecraft\mods on Windows and ~/.minecraft/mods on Linux, with the standard launcher) and compare. Look for a mod that is missing on one side, or present at two different versions.
4. In JAR Manager, note the Server software and Minecraft version. The player's launcher profile must use the same loader and Minecraft version.

Give players the exact mods

1. Open the Mods tab, which is under Content, and switch to Installed.
2. Press Export for players. The window "Export mods for your players" packs the mods players need into one zip, with a plain-English file that names the loader and where to put the mods.
3. Press Download zip and send it round. Players clear out their old mod files first, then unzip the new ones into the mods folder in their game folder.

Server-only mods are left out of the zip. If a player still gets the error, a mod the store lists as server-only may need to be on their side too. Reopen the window, tick that mod under "Left out" to include it anyway, and download again.

After you update a mod

A new version on the server is a new version players have to match. Press Check for updates in the Installed view, then Update all, restart, and export a fresh zip. Do not update on the server and leave players on the old files.

Still failing

• Check the loader as well as the mods. A Forge server needs Forge players, and NeoForge needs NeoForge. Which loader to pick explains why.
• If a mod will not start at all on the server, the message is different. Fix missing mods on a modded server covers it.
• Join a modded server from your launcher shows the player's side.