Minecraft Java 1.20.1 · Fabric
Pilotable mechs, Create contraptions and solar power. You install one mod — everything else downloads itself the first time you connect.
Printable instructions, a Word version, and the launcher pack file. Everything on this page is in there too — the download is just so you have it offline.
You never hunt down a mod file and you never match a version by hand. Setup takes about fifteen minutes, once.
Two things will stop you dead no matter how well you do the rest.
You need Minecraft Java Edition. The paid PC version from minecraft.net.
Bedrock Edition will not work — that’s the version on consoles, phones and the Microsoft Store. If pressing play shows you Realms or a Marketplace, you’re on Bedrock. No setting changes this. They’re different games.
You must be on the whitelist. Send Dan your exact Java username — the one in the top corner of your launcher. Spelling and capitals both matter.
If you’re not on it, the server refuses you with You are not white-listed on this server however perfectly you do everything below.
Use this route unless you already play other Fabric 1.20.1 mods — if you do, jump to the Prism route instead.
Go to fabricmc.net/use/installer, download the installer and run it. Set:
Minecraft Version: 1.20.1 Loader Version: leave it alone
Click Install. This adds a profile to your normal launcher. It doesn’t touch your existing game, your worlds, or anything you already play.
From modrinth.com/mod/automodpack — Versions tab, filter to 1.20.1 and Fabric, take 4.0.6:
automodpack-mc1.20.1-fabric-4.0.6.jar
From modrinth.com/mod/fabric-api — same filters, take 0.92.12:
fabric-api-0.92.12+1.20.1.jar
That’s everything you download by hand. The other mods arrive in step 5.
Windows — press Win+R, paste this, press Enter:
%appdata%\.minecraft
Mac — Finder → Go menu → Go to Folder, paste:
~/Library/Application Support/minecraft
Look for a folder called mods. If there isn’t one, make it — lowercase, spelled exactly that way. Drop both .jar files in.
Don’t skip this one. It’s the single most common reason the game misbehaves, and it looks exactly like the server being broken.
In the Minecraft Launcher:
Installations tab → find fabric-loader-1.20.1 → the “...” menu on the right → Edit → More Options → JVM Arguments
Find -Xmx2G near the start of that line. Change it to -Xmx8G and save.
If your computer has 8GB of RAM in total, use -Xmx6G instead. Never set it above half your total RAM. The mech models alone are a 50MB download and Create and Powah stack on top of them.
Use the dropdown next to the big Play button to pick fabric-loader-1.20.1, then press Play. At the title screen:
Multiplayer → Add Server Server Name: Mech Bay Server Address: mechbay.modded.fun
Click Done, then double-click Mech Bay to join. Read the next section first — two prompts are coming and they surprise people.
The first time you join you get two prompts. Both are normal. Neither means something went wrong.
A screen asks you to verify the server’s certificate or fingerprint. Accept it.
This is the sync mod confirming it’s talking to the real Mech Bay and not something impersonating it. You see this once, ever.
It offers to download the server’s modpack. Say yes.
It pulls roughly 200MB. The progress bar can look frozen on the mech models — they’re one very large file. Let it finish. When it asks to restart the game, let it.
After the restart, join again. This time you go straight in, and you never see either prompt again.
The main route shares one mods folder across everything on 1.20.1, so your existing mods would load alongside these and may fight each other. Prism Launcher keeps this server sealed in its own box.
From prismlauncher.org. The Modrinth App also works. The CurseForge app does not — it can’t open .mrpack files.
Add Instance → Import → choose Mech-Bay-Connect-1.1.0.mrpack from the download at the top of this page.
Right-click the instance → Edit → Settings → Memory → maximum 8192 MB. Then launch, sign in, and add the server as mechbay.modded.fun.
Your username isn’t on the list, or it’s on there spelled differently. Send Dan the exact username from your launcher, character for character.
Your Fabric Loader is too old. Re-run the Fabric installer from step 1 and let it install the newest loader for 1.20.1.
Almost always memory. Go back to step 4 and confirm the JVM Arguments line really says -Xmx8G. Changing it in the wrong installation profile is easy to do and looks identical.
Give it a full minute on the first attempt. If it times out, quit all the way out of Minecraft and try once more — the sync mod sometimes needs a clean start.
The modpack download didn’t finish. Leave the server, rejoin, and let the sync run again from the top.
Tell Dan what the screen said, word for word. The exact wording is what identifies the problem — a paraphrase usually isn’t enough to tell two very different failures apart.
-Xmx8Gmechbay.modded.fun