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Guides / Minecraft / Mods and modpacks

Update a modpack on your Minecraft server

Update an installed modpack from Add-ons, Modpacks. The panel backs up first, keeps your world and settings, and players must install the same pack version.

Updated , checked on Minecraft Java 26.3

When a new version of your modpack comes out, open Add-ons, then Modpacks. If a newer release exists, a button Update to and the version number appears next to the installed pack. The panel takes a backup first, replaces the pack’s files, and keeps your world and the settings you changed. Players then install the same pack version on their side.

This works for a pack the panel installed. A pack you put on the server by hand does not show up here.

In the ArthOS panel

  1. Open your server and choose Add-ons, then Modpacks.
  2. Under Installed modpack you see the pack name, its version, the loader and Minecraft version, and the number of files. If a newer release exists, the Update to button is on the right. It offers the newest release, not a beta (a beta only if the pack has no release). To move to a different version, search the same pack in Find a modpack and choose that version. The panel treats it as an update, because it is the same pack.
  3. Choose Update to. A window opens and reads the new version. The texts quoted below are what the panel’s window says: “Reading the pack: its loader, every file and its checksum. Large packs take a few seconds.”
  4. Before you go on, read the pack’s release notes. Mods the new version removes can leave their blocks and items missing from the world. Keep the backup until the world has loaded.
  5. Read the list under What will happen. For an update it says:
    • The server is asked to save and stop, if it is running.
    • A backup is taken first, so this can be rolled back. If every backup slot is full, it replaces the oldest backup the panel took before an earlier change, and the line names it.
    • The loader is installed for the pack’s Minecraft version and Java.
    • The new files are downloaded, six at a time, each checked against its checksum.
    • It replaces the files the old version placed that nobody has changed. Files you added stay.
    • Files made only for players’ screens are left out, because they stop a server from starting. The window lists them under Client-only files left out.
    • Files that cannot be fetched automatically are listed under Files it cannot fetch, with where to get them.
    • A warning if the pack usually needs more memory than the server has.
  6. Check the two options.
    • Keep configuration you changed is on by default. “The pack’s new settings files never overwrite ones already on the server.” Leave it on unless the pack’s notes tell you to reset a setting.
    • Start a new world is off by default for an update. “Not usually needed for an update. The current world stays in the backup.” Tick it only if the pack’s release notes say the old world will not load.
  7. If the panel cannot take a backup, it shows the reason and a box Continue without a backup (the panel’s label). If something then goes wrong there is nothing to roll back to, so free a backup slot first (see backups) rather than ticking it.
  8. If the panel asks you to accept the Minecraft EULA, tick that box too.
  9. Choose Update. The server is unavailable while this runs. Progress shows at the top of every page.
  10. When it finishes, start the server and read the first part of the Console for errors.

Tell your players

Players must join with the same pack version as the server. The window says “Players join with” the pack name and version “installed”, and links to the Pack page. Players update the pack in the CurseForge app or the Modrinth app, whichever they used to install it. See install a modpack for the first install.

Post the new version number where players will see it before you start the update, because they cannot join until they match.

By hand

Use this on any host.

  1. Take a backup of the whole server.
  2. Stop the server.
  3. Open the pack’s page on CurseForge or Modrinth and download the new server pack, if the author offers one. Read its release notes.
  4. Replace the pack’s files as the author says. Keep the world folder and any settings files you changed.
  5. Start the server and read the console.

If it does not work

  • There is no Update to button. You already have the newest release, or the panel did not install this pack. A pack installed by hand does not appear under Installed modpack.
  • The server fails to start after the update. Read the first error in the Console. If a mod now needs another mod or a newer loader, check the pack’s release notes. You can restore the backup the panel took first; the steps are in the backups guide.
  • Players cannot join. They are on a different pack version than the server. Have them update to the version in the window.
  • Some files could not be fetched automatically. The window lists them. Open each file’s page with Get it, upload it to the folder shown, and choose Check again. The panel accepts a file only if its checksum is the one the pack names.
  • The new pack was too big for the memory. The window warns when the pack usually needs more memory than the server has. A server that runs out of memory can crash when players join.

Not checked on 26.3 as of 11 October 2026: an update of a large pack on a 26.3 server.

Servers for all of this are on the Minecraft page.

Sources: minecraft.net: Eula

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