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Unstable SMP SimulatorMinecraft modpack for 1.21.11

All of the Unstable Simulators you'll ever need.

client and servernewest supported 1.21.11TechnologyAdventureOptimizationChallenging
Latest version
Vex-1.21.11-6.2
Minecraft
1.21 to 1.21.11
Java
Java 21+
Loader
Fabric
Licence
LicenseRef-All-Rights-Reserved
Downloads
74.2k
Updated
2 d ago
Available on
Modrinth
Space NodeOur hosting

Host Unstable SMP Simulator servers

One click and Unstable SMP Simulator is installed with the right loader, on hardware built for it.

  • 1.21.11
  • Fabric
  • One click modpack install
  • Dependencies handled
  • Tuned startup flags
  • NVMe SSD
Deploy a serverFrom €0.90 per GB

Minecraft versions

Every version Unstable SMP Simulator declares support for, newest first, with the Java runtime that version needs.

Other modpacks
MinecraftThroughJavaEvidenceReleased
1.21.11Fabric21+declared9 Dec 2025
1.21Fabric21+declared13 Jun 2024

Download

From Unstable SMP Simulator’s own host. Nothing is re-hosted here.

Vex-1.21.11-6.2release26 Jul 2026

UUSIM v2.mrpack · 483.7 MB · for 1.21.11

Download latest
b269144a269e…
Older versions20
  • Vex-1.21.11-6.123 Jul 20261.21.11473.1 MB2.8k downloads349de5c9c3e5…Get
  • Vex-1.21.11-6.023 Jul 20261.21.11464.7 MB243 downloads96a9ba0648b7…Get
  • Vex-1.21.11-5.023 Jul 20261.21.11499.3 MB69 downloadsa4f5abb6fa0b…Get
  • Vex-1.21.11-4.022 Jul 20261.21.11451.6 MB1.0k downloadscd95b0721cf8…Get
  • Vex-1.21.11-3.019 Jul 20261.21.11293.1 MB2.1k downloadsf988b1297322…Get
  • Vex-1.21.11-2.018 Jul 20261.21.11286.6 MB412 downloads2d1339d123c9…Get
  • Vex-1.21.11-1.115 Jul 20261.21.11223.0 MB1.8k downloadsd78ad684b0a8…Get
  • Vex-1.21.11-1.015 Jul 20261.21.11222.4 MB397 downloads7570371dbf88…Get
  • 1.21.11-3.124 Jun 20261.21.11161.0 MB8.5k downloads312a1126e13e…Get
  • 1.21-3.020 Jun 20261.21384.3 MB3.2k downloads7d7bbf7de003…Get
  • 1.21.11-3.020 Jun 20261.21.11489.1 MB830 downloadsfe212c887e65…Get
  • 1.21.11-2.412 Jun 20261.21.11343.2 MB2.5k downloads22b15aa3a74b…Get
  • 1.21-2.412 Jun 20261.21343.2 MB421 downloads45fb916c8ca2…Get
  • 1.21-2.315 Apr 20261.21330.4 MB1.4k downloadsdeffbc621880…Get
  • 1.21.11-2.115 Apr 20261.21.11330.4 MB453 downloadsb50a5e5b87af…Get
  • 1.21-2.215 Apr 20261.21330.4 MB206 downloads5aa2eb5c8d2f…Get
  • 1.21.11-2.015 Apr 20261.21.11330.4 MB191 downloadsb0ebe6f79f80…Get
  • 1.21-2.113 Apr 20261.21330.4 MB219 downloads0f1820eafaf7…Get
  • 1.21-2.012 Apr 20261.21330.4 MB310 downloadsa1dabe0a9af2…Get
  • 1.011 Apr 20261.21291.2 MB280 downloads7852a38173c9…Get

Frequently asked

Does Unstable SMP Simulator work on Minecraft 1.21.11?

Yes. 1.21.11 is the newest Minecraft version Unstable SMP Simulator declares support for, and the claim comes from the author's own release metadata rather than from a compatibility list somebody maintains by hand.

Which Minecraft versions does Unstable SMP Simulator support?

Everything the author has declared, from 1.21 up to 1.21.11. The full list is in the table above, with the Java runtime each version needs next to it.

Do I need to install Unstable SMP Simulator on the client or the server?

Both. Every player needs it installed and so does the server, so anyone joining without it will be refused.

Which loader does Unstable SMP Simulator need?

Fabric. A build for one loader will not load on another, so this is the first thing to check before the Minecraft version.

Which Java version do I need for Unstable SMP Simulator?

On the newest Minecraft release it supports, Java 21 or newer. The requirement comes from the Minecraft version you run rather than from the modpack itself, so on an older supported Minecraft the answer is that version's Java, not this one.

What licence is Unstable SMP Simulator under?

LicenseRef-All-Rights-Reserved, as stated by the author on the platform we synced it from. Check the project's own page before redistributing or bundling it.

How do I install Unstable SMP Simulator?

Use a launcher that imports packs, such as Prism Launcher, the Modrinth App or the CurseForge app, and open the pack file with it. The launcher installs the right loader and mods for you; installing a pack's mods by hand is the error-prone way.

Where do I download Unstable SMP Simulator safely?

From the author's own page on Modrinth, which is where the data here is synced from. MCReference never mirrors, re-hosts or repackages a file: every download button points at the original source, so you get exactly what the author published.

Works on the same versions

Ordered by how much of the recent Minecraft version coverage overlaps, not by popularity.

MAX FPS: Optimized🚀 MAX FPS WITHOUT UNNECESSARY MODS! Only 16 optimization mods - NOTHING EXTRA! ✅ ALL MAJOR VERSIONS ⚡ INSTALLS ON ANY LAUNCHER! (Guide below)PacktrixPre-packed Official Modpack containing Patrix Resource Pack for easy install using Fabric/Quilt.Simply Optimized ReloadedAn unofficial port of Simply Optimized built to support every major mod loader and stay current with the newest versions of Minecraft.ElixirA well-researched performance & optimization modpack to make the game run smoother! With shader & Fresh Animations support. 26.3 rc1 ✔fps+pvpFPS + PvP Boost is a lightweight Minecraft modpack designed to maximize performance and give players a competitive edge in PvP. With FPS-boosting optimizations and combat-focused tweaks, it delivers smoother gameplay, better responsiveness, and enhanced viJust Enough OptimizationJust Enough Optimization - Focused on low memory usage and higher avarege fps. Made for low-end pc so everyone can run Minecraft

Last checked 2 d ago against Modrinth. We do not host files and we do not republish descriptions; every download link points at the author’s own release.

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