Free Server Saver

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

If you've ever seen any of this 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, and to players that looks identical to network lag.

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

Five tiers. Static thresholds, hysteresis on recovery:

Heap Tier What changes < 60% 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 (getTarget() != null) — keep ticking at full rate
• Newly spawned (< 10 s) mobs — grace period
• Crops, leaves, snow, fire — random ticks are NEVER touched (Lithium handles those better)

Also addresses

• 4 GB world cap — /fss storage and /fss prune for the host's hard ceiling
• 10-minute startup limit — boot-time history + early warning if you're approaching it
• Metaspace OOM — RAM Boost extends heap, not Metaspace. We watch Metaspace separately and warn before the crash
• Chunk-generation lag — /fss pregen <radius> for spawn-area pre-gen (yields to Chunky if installed)
• 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 one is installed; bosses are never discarded)

Plays well with everything

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

• Lithium / FerriteCore / ModernFix — these handle static optimization; we handle adaptive throttle
• 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 (/fss, server-op only)

The short form is /fss; /freeserversaver works too as the full alias.

Command What it shows 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.

The translations are machine-generated as a starting point. Native-speaker corrections are very welcome — open a PR or issue.

What it does NOT do

• ❌ Network ping issues — that's geographical, no mod can help
• ❌ Bypass the host's idle-shutdown timer with fake players — that's exactly 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 to the MIT-licensed mods whose design patterns we adapted (Adaptive Performance Tweaks, ChunkPurge, Server Stasis) and the LGPL/GPL/ARR mods we studied for design context (Lithium, ModernFix, ServerCore, Where's my Brain, Immersive Optimization, DynView, OptimizeMod, Mobtimizations, Hibernateforge).

Unofficial community mod. Not affiliated with any hosting provider.