fragmentsPacks and mods
How a world states which mods it runs, and what the game does when yours do not match.
A world can carry a list of the mods it expects, and your game compares that list against what you have loaded before you are committed to anything. Nothing is installed behind your back, and the files come from Modrinth rather than from us.
Where the list comes from
- A world made on the site
- You chose the mods in the create wizard, or imported a Modrinth pack and edited it. That list is the world’s list from the start.
- A world made in the game
- Whatever you had loaded when you shared it becomes the list.
- Changed later
- The owner edits it on the world’s Pack tab. Everyone else picks the change up the next time they restart Minecraft.
- No list at all
- Perfectly normal. The mod does not force a world to state one, and a world with no stamped list never shows anybody this screen.
The screen you may meet on the way in
It sorts what you are missing into three groups, because the three want different things from you.
This world runs 24 mods. You have 21.
Can be downloaded from Modrinth:
You’ll need to install these yourself:
- Fetches the ones Modrinth can resolve straight into your mods folder. It cannot load them into a game that is already running, so a restart follows.
- Play anyway joins without matching. It is missing on the first visit to a world that has never been generated, for the reason below.
- YouPress Downloadseconds to minutes
- The gameThe files are fetched from Modrinth into your mods folderAnything Modrinth cannot resolve is listed separately for you to install by hand.
- YouRestart MinecraftJava loads mods at startup, so a mod downloaded into a running game does nothing until the next one.
- YouJoin againThis time the comparison passes and you go straight in.
Why the first visit is stricter
On a world that has never been generated, the screen has no Play anyway. Getting the mods is the only way forward, and it is the one place in the mod where you are blocked rather than warned.
The first time anybody plays a world, that machine generates the terrain. Mods that add biomes, ores or structures take part in that, and what they generate is written permanently into the ground. A player who generated the world without them would produce terrain the rest of the group could never match.
Checking without joining
/vbf pack[VBF] pack satisfied: all 24 mods present
The pause menu carries the same thing as a button whenever there is a difference, reading 3 mods missing or, once they are downloaded, 3 mods ready — restart to load.
If your launcher manages the instance
Editing the list as the owner
The Pack tab on the world’s page, which searches Modrinth filtered to NeoForge and Minecraft 1.21.1, and brings required dependencies along on its own. Saving replaces the world’s list, and everyone syncs to the new one on their next restart.
- The list carries what the mods are, not where to get them. Each player’s game resolves them itself.
- Adding a worldgen mod to a world that already exists will not retrofit the terrain that has already been generated.
- Everyone sees the list and its total size before they agree to download any of it.
How heavy a pack can be
A 777-mod pack has been run on the rig at full speed, measured on one machine. There is no throttle and no memory tier to buy, because the work is spread across the group’s own machines rather than a box somebody rents. What each machine has to do is set out on how it works.