XP Multiplier

Decide what XP is worth on your server. Per ore, per mob, per catch one config file, no restart, and nothing for your players to install.

What it does

XP Multiplier is a lightweight, server-side NeoForge mod that scales the experience players get from mining, killing mobs and fishing. Every source has its own multiplier, so you can hand out triple XP for diamond ore, cut zombie XP in half, make the Wither actually worth the fight and leave everything else exactly like vanilla.

Set a value to 1.0 and nothing changes. Set it to 0 and that source stops giving XP entirely. Anything in between works too - 2.5, 0.75, whatever fits your progression.

Why use this mod

Shape progression to fit your server - speed leveling up on casual or small-group servers, or slow it down for a harder survival grind.
Reward the activities you want to encourage - double XP from mining, reduced XP from easy mobs, a real payoff for treasure fishing instead of junk catches.
No client-side hassle - it's server-side only, so players don't install or configure anything; they just notice the game feels different.
Change your mind without a restart - the config is hot-reloadable, so you can tune values live and see the effect immediately.
Nothing breaks by surprise - every jar is built and locked to one specific Minecraft version, so it either loads correctly or doesn't load at all.

Features

Per-ore multipliers for Coal, Iron, Gold, Redstone, Lapis, Diamond, Emerald, Nether Quartz and Ancient Debris. Deepslate variants count as the same ore, so you only configure it once.
Per-mob multipliers for around 28 common hostile and neutral mobs - Zombie, Skeleton, Spider, Creeper, Enderman, Wither Skeleton, Blaze, Piglin, Warden and more.
Separate boss multiplier for the Wither and the Ender Dragon, so bosses don't get dragged along by the regular mob values.
Fishing multipliers with a base value plus separate values for the three vanilla loot pools: fish, treasure and junk. Reward treasure hunting without buffing rotten flesh.
Smelting multiplier for the XP you collect from a furnace, blast furnace or smoker. It scales the recipe's XP itself, so it also works for the cheap recipes that only pay a fraction of a point per item.
Enchanting cost multiplier for the levels an enchanting table charges. This one runs the other way round - higher means more expensive, 0 means free - and it is the only value that ignores the global fallback, so more XP on your server doesn't quietly mean pricier enchanting. Lapis cost and the level requirement shown on the slots stay vanilla.
Breeding multiplier for the XP a successful breed drops. Vanilla pays the same 1-7 XP whatever you bred, so this is one value rather than a list per animal - turtles, frogs and sniffers included, even though they lay an egg instead of spawning a baby.
Global fallback for every XP source that isn't listed individually.
Server-side only. Players join with a vanilla client and never notice the mod is there.
Hot-reloadable. Edit the config and reload it - no restart needed.

Config

The mod writes config/xpmultiplier-server.toml on first start. Every key is commented in the generated file, so you can see what you are changing without looking anything up.

[general]
    # Fallback XP multiplier for any source not explicitly listed below.
    globalMultiplier = 1.0

[ores]
    coal = 1.0
    iron = 1.0
    gold = 1.0
    redstone = 1.0
    lapis = 1.0
    diamond = 3.0      # triple XP from diamond ore
    emerald = 1.0
    quartz = 1.0
    ancientDebris = 1.0

[mobs]
    zombie = 0.5        # half XP from zombies
    skeleton = 1.0
    spider = 1.0
    enderman = 1.0
    witherSkeleton = 1.0
    # ... remaining standard mobs, see the generated file for the full list
    bossMultiplier = 1.0   # Wither / Ender Dragon

[fishing]
    fishingMultiplier = 1.0   # base value for every catch without its own value below
    fish = 1.0
    treasure = 2.0            # double XP for treasure catches
    junk = 1.0

[smelting]
    smeltingMultiplier = 1.0  # XP collected from a furnace, blast furnace or smoker

[enchanting]
    enchantingCostMultiplier = 1.0  # levels an enchanting table charges - higher = more expensive

[breeding]
    breedingMultiplier = 1.0  # XP dropped when two animals breed

Installation

Install NeoForge for your Minecraft version on the server.
Drop the matching jar into the server's mods/ folder.
Start the server once to generate config/xpmultiplier-server.toml, edit the values you care about, then reload the config or restart.

Clients don't need the mod. Players simply receive whatever XP the server hands out.

Compatibility with other mods

Ore and mob XP are changed through the standard NeoForge events, so other mods that modify XP for the same block or kill still get their say. Fishing loot the mod doesn't recognise, anything added by another mod, for example, is scaled with the base fishing value rather than being skipped.

Smelting, enchanting and breeding are handled with small mixins instead, because no event reaches those numbers in time. The smelting one scales the XP of whatever recipe was cooked, so recipes added by other mods are covered as well; the enchanting one scales the levels the table charges, and leaves the lapis cost and the level requirement on the three slots alone; the breeding ones sit where vanilla rolls the XP for a successful breed, so modded animals that breed the normal way are covered too.

Multi-XP