How much RAM do modpack servers really need? We boot-tested 29 packs

Every hosting company publishes “recommended RAM” for popular modpacks. Almost none of them have booted the pack on an actual dedicated server. We have — 29 packs and counting, each one installed on a fresh cloud VM, booted, and connected to before we let anyone pay for it. This page is the raw result: the measured RAM floor for every pack, and the 12 mods our tests caught crashing dedicated servers.

How these numbers were measured

For each pack: spin up a clean Hetzner VM, run the exact install path a customer gets, start the server, and wait for it to accept a real Minecraft connection. If it OOMs, we bump the container RAM and rerun. The number in the table is the floor that boots reliably and survives initial chunk generation — not the minimum that technically starts, and not a padded upsell number.

When a boot failed, we read the crash log, found the mod responsible, and encoded the fix into the install recipe. That’s why the table has a “fixes” column: those are real crashes you won’t hit, because the install applies the fix before first boot.

A nightly sweep re-tests stale packs, so a pack that breaks upstream gets caught and flagged automatically — here’s one it caught.

The full table

This table is generated from the same recipe registry our install pipeline runs — it updates automatically when new packs pass testing. Click a pack for the full breakdown of what its recipe fixes.

“Fixes applied” = server-crashing mods disabled + required mods added + server.properties pins + config overrides, all applied automatically at install. 35 fixes across 29 packs so far.

The mods that crash dedicated servers

These came out of real failed boots during testing. If you host anywhere else and one of these is in your pack, this list might save you an evening of reading crash logs:

• Essential_* — Essential is a client-side social/cosmetic overlay (gg.essential). Its EssentialTransformationService loads `org.apache.commons.codec.digest.DigestUtils` which is absent on dedicated server, FATAL ClassNotFoundException during boot (verified 2026-05-22).
• fancymenu_* — FancyMenu rewrites Minecraft's title/menu Screen classes — net.minecraft.client.gui.screens.Screen is NOT in DEDICATED_SERVER dist, so RuntimeDistCleaner aborts boot (verified 2026-05-22).
• melody_* — FancyMenu dependency, useless without FancyMenu (verified 2026-05-22).
• Controlling-* — Keybinding-conflict UI mod — touches client KeyMapping which doesn't exist server-side.
• entitytexturefeatures* — ETF client-side entity texture remapper — mixes into ResourceLocation with a handler that calls `net.minecraft.client.gui.screens.Screen`, FATAL on dedicated server (verified 2026-05-22 stack trace at `handler$zhh000$etf$illegalPathOverride`).
• configured-* — In-game config-UI mod, client-only.
• embeddium* — Vanilla rendering optimisation (client-only fork of Sodium for Forge).
• oculus-* — Shader loader, client-only.

Why “recommended RAM” numbers are usually wrong

Most published numbers are one of three things: the pack author’s client-side suggestion (servers behave differently), a hosting company’s upsell tier (“we recommend 12 GB” sells a 12 GB plan), or a forum answer from 2021. Server-side RAM demand depends on chunk generation, mob caps and simulation distance — things you only see by actually running the server and watching it.

Under-provisioning is the expensive mistake: the server boots fine, then OOM-kills during the first real exploration session with friends online. That’s why our signup auto-sizes RAM to the measured floor — you can’t accidentally order a configuration our tests have seen fail.