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Check Engine project artwork

CurseForge · Minecraft mod

Check Engine

Your modpack's check engine light. Crash, missing mod, broken recipe or "Invalid player data" kick? It tells you what broke and how to fix it, in plain English. Undo bad updates, find the faulty mod, back up and rescue your worlds. Never touches gameplay.

Choose a version Pick your version below, then grab the matching file.

Quick answer

Which Check Engine release matches 1.20.1 Forge?

Updated yesterday
Best match for your filters Check Engine 0.24.0 (Forge 1.20.1)
Game version 1.20.1
Loader Forge

Check Engine 0.24.0 (Forge 1.20.1) targets 1.20.1 with Forge. The project page does not say whether this file belongs on the client, dedicated server, or both. No extra mods listed for this file.

Where it goes

Is Check Engine required on the client, server, or both?

The project page does not say whether this file belongs on the client, dedicated server, or both.

Client Source doesn’t say
Dedicated server Source doesn’t say
Loader for this release Forge
Required install it here Optional supported, not mandatory Not supported do not install here Source doesn’t say do not assume

The source does not explicitly classify this release as client-only or server-only.

Understand client and server requirements Read the Minecraft installation guide

What else does Check Engine 0.24.0 (Forge 1.20.1) need?

Check Engine 0.24.0 (Forge 1.20.1) on 1.20.1 Forge. Every mod below is checked against that same setup.

No extra mods listed for this file

This file does not list any required mods. Do not add a library just because a different file uses it.

This file does not list any required or optional mods.

Before you install it

Add Check Engine without breaking your instance.

Built for Check Engine 0.24.0 (Forge 1.20.1) on 1.20.1 Forge. Pick another file and the loader, install side or required mods may change.

  1. 01

    Stick to this file

    Use Check Engine 0.24.0 (Forge 1.20.1). It targets 1.20.1 with Forge; another release may have different loader, side or dependency requirements.

  2. 02

    Bring the mods it needs

    This file does not list any required mods. Do not add a library just because a different file uses it.

  3. 03

    Put it on the correct side

    The project page does not say whether this file belongs on the client, dedicated server, or both.

  4. 04

    Pick the file you checked

    Use the “Get this file” button beside Check Engine 0.24.0 (Forge 1.20.1). It opens that exact file at the source.

About this project

What does Check Engine add?

Check Engine: your modpack's warning light

GitHub NeoForge Forge

Modpack broke after an update? One button puts it back the way it was.
Check Engine finds why your modpack crashes or won't start, tells you the fix in plain words, and can undo what broke it.

Won't start? Know before the long load

The Check Engine window, shown before the loading screen

Press Play and get Exit code 1? Check Engine stops it right away: which mod is missing or wrong, and the fix.

Broke after an update? Go back

Go back to when it worked: the list of what changes, and Put it back

Go back to when it worked turns off new mods, brings back the old version of updated mods, and puts your configs back. Nothing is deleted, and Put it back undoes it.
Making your own modpack? Mods only keeps your config work.
Goes back to the last launch that worked with Check Engine installed.

Crashed? Mechanic

Mechanic with tabs: Fix, Crash lines, Changed, Get help

The next launch explains the crash: the cause and the fix, or "not sure" instead of a guess. Copy for help puts it all on your clipboard for your modpack's Discord, with your name, IP and login blanked.

Already crashed? Add Check Engine and press Play: it reads the last crash too.

Never deletes anything. Never goes online. Touches your mods only when you press a button. Works next to other crash helper mods.

Everything it does

Feature What it does How to use it
Pre-launch check Stops a broken modpack before the long load: which mod is missing or wrong, and the fix Automatic when you press Play
Go back to when it worked Turns off new mods, brings back old versions and removed mods, puts configs back. Nothing deleted Pre-launch window, Mechanic > Fix, or the title button > Go back. If configs changed too, pick Mods only or Mods and configs
Put it back Undoes a Go back In game right after Go back, or the title button > Go back > Put it back
Mechanic Explains your last crash: the fix (or "not sure"), the key crash lines, what changed Automatic on the next launch after a crash
Copy for help Everything a helper needs on your clipboard, name, IP and login blanked Mechanic > Get help > Copy for help, then paste in your modpack's Discord. With another crash helper mod installed, use its window instead
Help file One zip with the reports and logs, name, IP and login blanked Mechanic > Get help > Make help file, or type /checkengine export
Help Help button on every screen: what is this screen, copy for help, your modpack's help page Bottom left on every Check Engine screen and on the pre-launch window
Misfire (Beta) Finds the mod behind a crash by switching mods off, a round at a time Mechanic > Fix > Misfire, then keep launching until it names the mod
Pit Stop Start time, last launches, what changed, every mod by blocks, items and size Click the Check Engine button on the title screen, or Mods > Check Engine > Config > Open Check Engine
Slower start Tells you once when the game started clearly slower than usual, and what changed Automatic. The title button shows ↑
Startup warnings Duplicate mods, known clashes, mods for a newer Java, client-only mods on a server Automatic, before the title screen. Press Got it to hide one
Only tell me when it breaks No more warnings, just crashes and problems that stop the game Press it on the warning screen. Turn back on: Mods > Check Engine > Config > Turn warnings on
World backups Warns before a world opens without a mod it uses, or after a mod went back a version Press Back up worlds or Back up these worlds when the warning shows
Can't join (Beta) Names the mods that don't match the server Press Fix it on the can't-join screen, Undo to put them back
/checkengine scan Lists recipes and quests that use missing mods Type it in chat (needs cheats on, or op on a server), then click [Open report]
Check Pack.bat Checks a modpack without starting the game (Windows) Get it from Releases with the checkengine-cli jar, keep both in one folder, drag your modpack folder onto it

For modpack makers

You decide what your players see. It's all in config/checkengine-pack.properties, and Check Engine only reads that file, it never changes it.

  • Switch off any part: set ignition (windows before the game loads, startup warnings), mechanic (crash screen), pit_pass (help when a server kicks a player), misfire (search for the faulty mod), scrapyard (world backup warnings) or pit_crew (/checkengine scan, update notes) to false. Leave a line out and that part stays on.

  • mode=modpack: players only see what stops the game, crashes and world backup warnings. Everything else stays in checkengine/boot-report.txt and Check Pack.bat for you.

  • Example file: config/checkengine-pack.example.properties lists every setting, including your modpack's name and Discord link for Check Engine's screens. Copy it to checkengine-pack.properties to use it.

  • Leave the checkengine/ folder out of your export.

  • NeoForge 26.1.2 (Java 25) · NeoForge 1.21.1 (Java 21) · Forge 1.20.1 (Java 17). Client, server or both.

  • Modpacks: yes, please. MIT licensed.

Wrong answer or missed crash? Press Report it in Mechanic, leave a comment, or open an issue.

Project description from CurseForge.

Pick your setup

Check Engine by Minecraft version and loader

Choose the version and loader you play, then open the matching release.

3 available setups

Check the dependencies, then try the file in a copied instance before changing a world you care about.

Recent files

Check Engine versions and loaders

14 of 43 releases match
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