Free Server Saver

Lag reducer for low-RAM Minecraft servers (Falixnodes, Minehut, self-hosted) — anything stuck on 2-4 GB of RAM.

The problem

If you've seen any of these on your server, it's the same root cause:

Mobs teleporting 5-10 blocks instead of moving smoothly
You and a friend get disconnected even though only 2 people are online
The server freezes for half a second every few minutes
"Server crashed because it ran out of memory" after a fine hour of play
"OutOfMemoryError: Metaspace" even though RAM Boost is active

All of those are GARBAGE COLLECTION PAUSES. Your host gives you a small heap, modpacks fill it, the JVM stops the world to clean up. To players, that looks identical to network lag.

The fix

Free Server Saver polls heap pressure every 2 seconds and gradually scales back AI ticks, mob spawns, view distance, and chunk loads BEFORE the heap fills. No GC pause, no rubber-banding, no disconnects.

How it works — 5 tiers, hysteresis on recovery

BELOW 60% heap — NORMAL — vanilla behavior
60-70% — L1 — far mobs tick every other tick; 50% of natural spawns rejected
70-80% — L2 — distant mobs at 1/8 tick rate; all natural spawns rejected
80-85% — L3 — view distance compressed to 6 chunks
85%+ — L4 EMERGENCY — distant mobs force-discarded; server tick rate halved

When the heap recovers, every change reverses automatically.

Protections — what stays normal even at L4

Bosses (EnderDragon, Wither, Warden, Elder Guardian, Ravager, Hoglin, or anything with >80 max HP)
Villagers, wandering traders, golems, allays — your iron farm and trading hall keep working
Named, leashed, tamed, persistent mobs
Combat-engaged mobs — keep ticking at full rate
Newly spawned (< 10s) mobs — grace period
Crops, leaves, snow, fire — random ticks are NEVER touched (Lithium handles those better)

Also addresses

4 GB world cap (free-host hard ceiling) — /fss storage to watch, /fss prune to identify pruneable chunks
10-minute startup limit — boot-time history + early warning
Metaspace OOM — RAM Boost extends heap, not Metaspace. We monitor it separately
Chunk-generation lag — /fss pregen <radius> for spawn-area pre-gen
Mob-farm detection — opt-in scan that flags chunks with 30+ same-type mobs
Stuck-entity crashes — entities / block-entities that throw the same tick exception repeatedly are auto-quarantined before they crash an unattended server (yields entirely to Neruina / Bug Fix Mod / Failsafe if installed; bosses are never discarded)

Plays well with everything

Free Server Saver detects competing performance mods and yields rather than fighting them. Install side-by-side with:

Lithium, FerriteCore, ModernFix — these handle static optimization; we handle adaptive
Adaptive Performance Tweaks, Tick Dynamic, Tick Tweaks — we yield to their tick-time logic
Where's my Brain, DAB, OptimizeMod, Immersive Optimization, No See No Tick — we yield to their distance throttle
Chunky — we yield our pregen command to its better one

The startup log shows which modules yielded and why. No double-throttling, no /tick rate fights, no surprises.

Commands

All under /fss (or the full alias /freeserversaver), op-only (permission level 2):

help — all subcommands with descriptions
status — current tier + heap percentage
metrics — heap, tier, players, chunks, view distance
history — last 20 tier transitions, color-coded
env — JVM heap/CPU snapshot from server start, with RAM Boost detection
lagspikes — recent 100ms+ ticks with heap state at the time
top entities — top 10 entity types by count
inspect chunks — per-dimension loaded / forced / player counts
tuning — current AutoTuner threshold offset
prune — identify unreachable loaded chunks (flood-fill)
storage — world directory size vs the host's 4 GB cap
pregen <radius> — pre-generate chunks around you
quarantine — recently quarantined entities / block-entities

Languages

Output translated to 9 languages: English, 日本語, Deutsch, Português (BR), Español, 简体中文, 한국어, Français, Русский. A Japanese client sees Japanese on a server in any locale.

Translations are machine-generated as a starting point. Native-speaker corrections are very welcome — open a PR or issue on GitHub.

What it does NOT do

Network ping issues — geographical, no mod can help
Bypass the host's idle-shutdown timer with fake players — that's what many free hosts ban (Carpet). Free Server Saver works within the host's rules

Requirements

Minecraft 1.21.1
NeoForge
JDK 21

(1.21.2+ port pending — vanilla's random tick logic changed in 1.21.2 and we want to validate first.)

Companion mods (strongly recommended)

For a complete low-RAM stack, install alongside:

Lithium — allocation-cheap optimizations across the engine
FerriteCore — 40-50% block-state memory reduction
ModernFix — mod-loading speedup; helps with that 10-minute free-host boot limit

Free Server Saver intentionally stays out of their lane. They handle static optimization, we handle adaptive response.

License & attribution

MIT. See NOTICE.md in the GitHub repo for full attribution.

UNOFFICIAL community mod. Not affiliated with any hosting provider.