Mods/Installing mods using ModLoader

Caution when using Mods in Minecraft
Before you decide to mod your copy of Minecraft, it is very important to understand what you are doing or you may end up messing up your copy. (If your copy of Minecraft is compromised, you can always backup your worlds and re-download Minecraft) Let me repeat that for you: If you mod Minecraft, you may break your copy of the game as well as any worlds that you play in. Because you are doing something that is wholly unsupported by Mojang, they won't be able to help you. Additionally, the authors of the mod make no guarantees as to whether or not the code works, much less any guarantees of support. Additionally, due to how modding works, updating Minecraft will break your mods but not the worlds you played in (any mod items in your world will not be present).

Installing Mods prerequisites

 * Knowledge of Zipping/Unzipping files, and working with a good archive utility (such as WinRAR, 7zip, etc.) or knowledge of Mod Installer to install mods automatically.
 * Knowing how to submit proper bug reports.
 * Knowing how to actually install the mod and its prerequisites.
 * Knowing how to accurately read and follow instructions

You might be able to get away without knowing how to do a few of these things, but if your copy of Minecraft breaks, then you should seek help from somebody in the modding community (preferably the mod author). If you view this as a great opportunity to learn something new, then you're on the right path!

How do Mods work
There is a file on your computer called "minecraft.jar" that provides everything Minecraft needs to be able to run. For example: world generation, showing blocks, managing mobs, items, and recipes. When you add mods to Minecraft, you are taking Minecraft.jar and over-writing it with the changes needed. All of these files inside of minecraft.jar that make it run are run through a process called "obfuscation". Basically what that means is that it changes the word "recipe" to the word "bf" (for the technically minded, all class names, variable names and identifiers are turned into one or two letter nonsense names).

Further, each entity in the game (a Mob, Item, Block, etc.) has an ID so they can be described on the map. As new content is added to Minecraft, new IDs are used, so you have to be careful that the Floodgate mod you just installed doesn't conflict badly with the new update of Minecraft that added Repeaters.

This has a few very important implications: If the mod that you wish to install involves neither of these actions then you should feel quite secure. If not, a good measure of safety is to only install very popular mods. Risugami created the Modloader and other great, safe, and popular mods; and the new version made modding much more safe. Read comments on mod posts before downloading and installing)
 * This is fundamentally changing the way Minecraft was meant to be played. So Notch, and Mojang AB will not be able to help you in any way, and are no longer responsible for crashes, data loss, etc.
 * Some mods might claim to do something like add a cute puppy to your world, but could in fact have been authored with a malicious intent such as stealing your Minecraft username/password, or install a keylogger. This is only a concern if...
 * The mod that you download contains an executable and you run it.
 * The mod that you download informs you that you should modify the Minecraft launcher (Minecraft.jar generally in the main application directory; not the 'minecraft.jar' described below.
 * When Minecraft is updated, all mods need to be re-updated by their authors, because Mojang obfuscates the source. If a mod uses an ID number that Mojang chooses to use in the update, this will cause further issues, and your world will look weird, or potentially be completely broken and unusable. Mod authors do this of their own free will, and it can take weeks for them to update. However, this doesn't mean you should harass the author about it.
 * If two mods do similar things, they will likely be incompatible, because they both will try to change the "bf" (or "recipe") file. (This can be fixed, nowadays mods also come with a properties file to change block and item ID's to fix conflicts.)
 * You may be adding new entities to your worlds, so if you ever have to remove the mods (say because of a Minecraft update), that world will no longer be compatible.

How to find your minecraft.jar file
You will see minecraft.jar (It may appear only as minecraft)
 * Windows ME/95/98/XP:
 * 1) Click start.
 * 2) Click Run....
 * 3) Type %AppData%.
 * 4) Open .minecraft.
 * 5) Open bin.

You will see minecraft.jar (It may appear only as minecraft)
 * Windows Vista/7:
 * 1) Click the Start Icon.
 * 2) In the Search Bar, type %AppData% and press Enter.
 * 3) Open Roaming.
 * 4) Open .minecraft.
 * 5) Open bin.

You will see minecraft.jar
 * Macintosh:
 * 1) Click Finder.
 * 2) From Places, choose your Username.
 * 3) Open Library.
 * 4) Open Application Support.
 * 5) Open minecraft.
 * 6) Open bin.

You will find minecraft.jar located in ~/.minecraft/bin/. From Nautilus (or most other file browsers), press Ctrl+H to see hidden folders the navigate to .minecraft. If in the console, type, ls -a ~/ and you will find the .minecraft directory.
 * Linux:

On most operating systems you can select the texture packs button on minecraft's main menu which will open the minecraft folder. Click 'up' from there and you will be in the .minecraft directory.

Making backups
If you simply want to test a mod without any risk, simply backup .minecraft in its entirety. Restoring it will revert everything to a pre-modded state (including your worlds).

If you are going to mod in a more persistent and complex fashion then you should keep the following recommendations in mind:


 * Back up your worlds in .minecraft/saves
 * If you have had previous mods installed, back up the minecraft.jar too, so as not accidentally uninstall mods.
 * If you wish to potentially keep your stats and achievements safe, backup the directory .minecraft/stats
 * Do not put custom mod only items in chests if you wish to access that world again from an unmodified version of Minecraft. It is possible that if you do so, when you remove the mod and then try to open or smash the chest, Minecraft might crash.

Backing up your worlds should be done every time you install a new mod.

ModLoader, Spawnlist and friends
mod authors will give a configuration file to change item ID's. Find the conflicting ID, and change it. Just remember that when an update for minecraft or for the mod comes out, you must use the same item ID's, or suffer the crashes.
 * There are many mods that absolutely require other mods to work, because they use some of the commands these other mods give. These are also known as utility mods. These mods include ModLoader (for adding mods in general), AudioMod (for adding sounds), ToolUtils (For making specific tool functions), spawnlist (for adding new mobs) and Turbomodel (for more advanced models). These mods that are required by some mods will need to be installed with the mod before Minecraft is run. Without them, the mod will not work and can even lead to Minecraft crashing.

Dealing with your first crash

 * Running minecraft in command line mode to get a stack trace.
 * Posting this stack trace as an error report on the mod authors website/forum/thread.
 * If using ModLoader, check the log (modloader.txt) in the .minecraft folder for errors.
 * If you cannot fix the crashing, refer to the next section to restore your Minecraft and worlds.

Deleting Mods, fixing crashes, and restoring Minecraft
There are 2 ways to delete a mod. 1. (only if mod is installed this way) Go into the mods folder in the .minecraft folder and remove the mod from the folder. (Later versions of Modloader only) 2. Restore your version of Minecraft, making sure to keep your worlds.

To restore minecraft, go to the APPDATA folder. Go into Roaming. Move your .minecraft folder onto the desktop. (or wherever you wish) Open the Minecraft Launcher, making sure your username and password are correct and log in. The Minecraft Launcher will then download a new, fresh .minecraft folder into the Roaming folder. Once it is done, open your modded .minecraft folder. Go into the Saves folder. Do the same for the fresh, no mods .minecraft folder. Take your worlds from the modded .minecraft folder and put them into the saves folder in the fresh .minecraft folder. Your worlds should be fine, but any mod items in your world will disappear.

To fix a crash, consult the following problem solving list:

- Did you delete the META-INF folder in minecraft.jar?

- Forgot ModLoader?

- Do your mods have conflicting item or block IDs? If so, most mods have a properties file to change the block and item IDs. - Look in modloader.txt to see what block ID(s) are conflicted.

- Is the mod made for your current version of Minecraft?

- Did you install any/all dependencies for the mod? For example, TurboModelThingy is required for the Planes Mod to work, and ModLoaderMP is required with Modloader for SDK's Guns Mod.

- Do you have the right version of Modloader?

- Do you have the right version of the mod?

- Are you SURE you installed the mod correctly? (consult any README file in the mod)

How to effectively get help

 * Delete the META-INF folder.
 * Check to make sure there are no conflicting mods.
 * If using a Modloader mod, make sure the correct version of Modloader is installed.
 * Check the version of your mod.

Installing your second Mod, testing for compatibility.

 * Open your "minecraft.jar" folder (How to Find Your minecraft.jar File) with an archiving utility such as WinRAR or 7-Zip, and drag the mod files from the folder you downloaded, to the minecraft.jar folder. Most mods require the folder "META-INF" inside of minecraft.jar be removed before the mod can work.

Dealing with crashes
Installation de mods
 * Your mod may be conflicting with block or item IDs. Check the place you got the mod to see if anyone else is having the same errors, and see if there is a solution.
 * You may have forgot to delete your "META-INF" folder. Most mods require that this folder be removed before loading the mod will work.
 * Risugami's Modloader and other mods such as Audio Mod will really help if the mods keep crashing(or if minecraft is muted without your own will)