Mods/Installing mods using ModLoader

Caution
'Before you decide to mod (modify) 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)' 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.

Due to how modding works, updating the Minecraft client will break your mods. That is, with each update of the Minecraft client, you will have to obtain updated mods and re-install them. However, the worlds you created will not be destroyed (although any mod items in your world will not be present).

Additionally, the authors of the mod make no guarantees as to whether or not the code works, much less any guarantees of support.

Nearly all mod packs have auto-installers that make adding mods to Minecraft extremely easy for the beginner Modder. You can search for mod packs on the Mods page.

Prerequisites
You should always know the prerequisites first, else the whole mod might not work. Here is a list of prerequisites you must have: 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!
 * Knowledge of zipping/unzipping files, and working with a good archive utility (such as WinRAR, 7-Zip, etc.).
 * Knowing how to accurately read and follow instructions.
 * Knowing how to submit proper bug reports.
 * Knowing how to install the mod and its prerequisites.
 * Knowing which mods conflict with each other and which do not.
 * Making sure you reread the instructions.

Note: You can use Forge or MCPatcher to do some or all of this work for you!

How Mods Work
A  file on the versions folder under .minecraft provides everything Minecraft needs to be able to run. When you add mods to Minecraft, you are taking the  file and over-writing it with the changes needed. All of these files inside run through a process called obfuscation.

Furthermore, everything in the game (mobs, items, blocks, etc.) has an ID which allows the game to differentiate each of them. As new content is added to Minecraft, new IDs are used.


 * Notes
 * This is fundamentally changing the way Minecraft was meant to be played. So Mojang will not be able to help you in any way, and are not responsible for crashes, data loss, etc.
 * Some mods might claim to do something, 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
 * 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 mods from a secure and safe website. Make sure to read the comments on mod posts before downloading and installing.


 * When Minecraft is updated, all mods need to be re-updated by their authors and re-downloaded and placed into the folder, because the launcher downloads a legit copy of Minecraft from Mojang when it updates. If a mod uses an ID number that Mojang uses in the update, this will cause further issues, and your world might 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 will both try to change the same thing (this can be fixed; nowadays, mods come with a properties file to change block and item IDs 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.

Downloading Mods
Always be careful when downloading mods. Make sure you download them from the original source to minimize the risk of viruses and be careful with running anything you download on your computer.

ModLoader, Spawnlist and friends
There are many mods that absolutely require other mods to work, because they use some of the commands these other mods give. These are known as utility mods. These include ModLoader (for adding mods in general), and Minecraft Forge, which is a more advanced ModLoader. 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. A much more list of mods can be found here.

Mod authors may give a configuration file to change item IDs. Find the conflicting ID, and change it. Just remember that when an update for Minecraft or the mod comes out, you must use the same item IDs, else the game will crash.

Making Backups
If you want to test a mod without any risk, simply backup .minecraft. 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 in mind:
 * Back up your worlds at
 * If you've had previous mods installed, back up the  file too, so as not accidentally uninstall mods.
 * If you wish to potentially keep your stats and achievements safe, backup the directory
 * 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 break the chest, Minecraft might crash. If you do this accidentally, you can stand on top of the chest, and type in . It will remove the chest and the items inside it without crashing the game.

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

Before 1.6
Windows:
 * 1) Press.
 * 2) Type in.
 * 3) Open bin and you will see minecraft.jar.
 * 4) Open the   file using an archive software (recommended WinRAR). To do this, right-click on minecraft.jar and hover to the Open With menu item.
 * 5) Copy the class files into this folder. Exit the folder once you have copied the class files.
 * 6) Certain mods will require you to copy files into other directories. Follow the instructions on your download for clarification on where to copy files to.

Mac:  Go to Applications > Utilities and open Terminal. Type in the following, line by line: cd ~ mkdir mctmp cd mctmp jar xf ~/Library/Application\ Support/minecraft/bin/minecraft.jar Outside Terminal, create a folder named mctmp. Copy all the files and folders into the mctmp directory. Back in Terminal, type in the following: rm META-INF/MOJANG_C.* jar uf ~/Library/Application\ Support/minecraft/bin/minecraft.jar ./ cd .. rm -rf mctmp 

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


 * 1) Navigate to the bin folder.
 * 2) Open the   file using an archive software.
 * 3) Copy the class files into this folder. Exit the folder once you have copied the class files.
 * 4) Certain mods will require you to copy files into other directories. Follow the instructions on your download for clarification on where to copy files to.

Any OS: On most operating systems, you can click the Texture packs button on Minecraft's main menu which will open the .minecraft folder. Simply navigate to the parent folder to get into the root of the .minecraft directory.

1.6 and above
It is recommended to install mods via Minecraft Forge when installing mods for Minecraft 1.6 and above.

Dealing with Crashes

 * Running Minecraft in command line mode to get a stack trace.
 * Posting the stack trace on the website/forum/thread of the mod author(s).
 * If the game still crashes, refer to the next section to restore your Minecraft and worlds.
 * Restart Minecraft.

Fixing Minecraft
If you have encountered a crash like above, then this section might help you.

Deleting Mods
There are three ways to delete mods from Minecraft.
 * 1) Go into   and remove the mod from the folder. If the mods folder does not exist, then refer to the next way.
 * 2) Restore your version of Minecraft, making sure to keep your worlds.
 * 3) Force update. You can do this by deleting the   file and re-downloading the game from the launcher.

Fixing Crashes
To fix a crash, consult the following problem solving list:
 * Have you deleted the META-INF folder inside the  file?
 * Forgot ModLoader?
 * Do your mods have conflicting block or item 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. If the file does not exist, then you have not used ModLoader.
 * Is the mod made for your version of Minecraft?
 * Have you installed the dependencies for the 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)

Restoring Minecraft
If you have backed up your .minecraft folder, then you have to delete or remove the modded .minecraft folder and placing the backed up folder into where you have deleted the modded folder.