Paper, Fabric or NeoForge
The first choice in Add a server is the software, and it decides what your server can load. The short version: plugins run on Paper and its relatives, mods run on Fabric and NeoForge, and you cannot mix the two on one server.
Start here
| You want | Choose |
|---|---|
| A server for you and friends, with plugins, and no fuss | Paper |
| The same, with more settings to tune | Purpur |
| Nothing added, exactly as Mojang ships it | Vanilla |
| Mods that change the game | Fabric |
| Mods built for NeoForge | NeoForge |
| A ready-made modded world | A modpack (how) |
| A big server with lots of players spread across a large world | Folia (with care) |
| Slime world formats, built in | Advanced Slime Paper |
If you are unsure, take Paper. It is SpawnLoft's default, it downloads and verifies itself, and it is where most plugins live.
Plugins or mods
| Plugins | Mods | |
|---|---|---|
| What they do | Add features and rules to the server | Change the game itself |
| Do players install anything? | No, they join with normal Minecraft | Usually yes, the same mods on their side |
| Runs on | Paper, Purpur, Folia, Spigot, CraftBukkit, Advanced Slime Paper | Fabric, NeoForge |
| In SpawnLoft | The Plugins tool | The Mods tool |
That second row is the deciding one for a server of friends. With plugins, everyone joins with plain Minecraft. With mods, everyone needs to match.
The software, one by one
Paper is the sensible default. It runs Bukkit and Spigot plugins, SpawnLoft searches Modrinth and Hangar for it, and it downloads from PaperMC with a checksum.
Purpur is a Paper fork with more configuration. It loads the same plugins. Pick it when you find yourself wanting a setting Paper does not have.
Folia is Paper with the world split into regions that run on separate threads. It is aimed at very large servers, and it only loads plugins built for it. Most plugins are not, so check before you commit.
Advanced Slime Paper is Paper with Slime World Manager built in, for servers that store worlds in the Slime format.
Spigot and CraftBukkit are compiled on your machine by BuildTools, because SpigotMC publishes no jars. That needs a JDK, takes five to ten minutes the first time, and uses about 1 GB of disk. Paper does the same job with none of that, so choose these only when you need them.
Vanilla is Mojang's own server. It loads nothing, and the Plugins tool says so.
Fabric is a mod loader. SpawnLoft installs the launcher and searches Modrinth for mods for it.
NeoForge is a mod loader too, and the two are not interchangeable: a mod is built for one or the other. SpawnLoft runs NeoForge's installer and searches Modrinth for mods for it.
A modpack builds a whole server from a Modrinth pack in one step. See running a modpack server.
Java takes care of itself
Each server picks its own Java. A Minecraft 1.20.4 server uses Java 17, 1.21 uses 21, and 26.x uses 25. SpawnLoft picks the newest installed Java that fits when the server is created, and refuses a version nothing installed can run before it downloads anything, with a link to the one it needs.
Changing your mind
You can update within the same software, and move to a newer Minecraft version, from Settings → Server software. Moving between kinds of software is a new server: create it, and bring your world across. Paper, Purpur, Folia and Advanced Slime Paper can upgrade in place; the others change version by creating a new server or importing a newer jar.
The full list, with sources and how each is verified, is in server software.